What is language?
Language is a way of communication. A
characteristic style of speech or writing that interacts between two mediums
that is user and machine. A set of characters convention and rules that is used
for conveying information is called Language.
What is program?
A well-define set of instructions given to computer
is called program. A computer program is written in a programming language.
What is programming?
Programming is the process of writing computer
based programs or software. Creating of a computer program is called
programming. The steps are
Preparing
the necessary documentation.
Writing
the program logic.
Developing
the program.
Assembling,
compiling or interpreting the program.
Testing
and debugging the program.
What is programming language?
A set of words and symbols used to write a program
is called programming language. The programming languages are used to write
computer program. A programming language is a means of communication between a
user and computer. In other words programming language is a complex synthetic
mechanism which provides some special features to build/develop any
program/software are called programming language. All the computer software is
written in a special type of computer software called the programming
languages.
What are the types of programming languages?
There are two major types of computer programming
languages:
Low Level
Languages
High
Level Languages
What are
the low level languages?
A low level language that is very closer to the
computer hardware. The term low level means closeness to the way in which the
machine has been built. Low levels are machine oriented languages and required
extensive knowledge of computer hardware and its configuration. The low level
languages are divided into machine language and assembly language.
What is the machine language?
A type of language in which instructions are
written in binary form called machine language. It is the only language that is
directly understood by the computer. It doesn’t need any translator program. We
also called it machine code and it is written as string of binary (1s or 0s).
It is at the native language of the computer. A program written in machine
language can be executed very fast by computer. The computer does not need any
translator to understand this language. The programs written in machine
language are machine-dependent. Every computer has its own machine language. A
program instruction may be like this 100110101. It is not an easy language for
you to learn because of its difficult cods and it is also difficult understand.
It is efficient for the computer but very inefficient for the programmers.
What is the assembly language?
A programming language that is one step away from
machine language means to say that it is first step to improve the programming
structure. In assembly language, machine instructions are replaced with
English-like word known as mnemonics. It is pronounced as Ne-Monics. Assembly
language is mostly used for writing system software. Programs written in
assembly language are easier to write and modify than machine language.
Assembly language is requiring translating program
to translate assembly language into machine language. The translator program is
called “assembler”.
What are
the high level languages?
High-level
languages are programming languages that are more user friendly, to some extent
platform to independent and abstract form low-level languages. In high-level
languages we can’t directly interact with the hardware. Assembly and machine
language require deep knowledge of computer hardware. Where as in high-level
languages you have to know only the instruction in English words and logic of
the problem irrespective of the type of computer you are using. High level
languages are simple languages that use English and mathematical symbols like
+,-,*, / etc for its program creation. In high level languages we use compiler
or interpreted to translating our program. The high-level languages enable to
the programmer to write the program the English words, but these English words
cannot be understand by the computer, so special types of translators
(compilers, interpreters) are required that convert the high level language
program into the machine readable format (machinery language program) that can
be read by the computer without any further translation. There are different
types of the high-level languages, such as: BASIC, FORTRAN, COBOL, PL/1, VB,
Pascal, ALGOL, Ada
What are the characteristics/advantages of high level languages?
Some important characteristics or advantages of
high-level languages are as follows:
Easy to Learn:
High-level Languages are closer to human languages and far from machine
language. These are English like language and are easier to learn.
Easy Error Detection: High-level languages are easy to read and modify. It makes it easy to
find error in programs written in these languages.
Standardized Syntax: The syntaxes of high-level languages are standardized. These languages
described a well-defined way of writing programs. Different organizations work
to determine standard syntax of these languages. An important organization is
American National Standard Institute (ANSI).
Deep Hardware Knowledge not Required: These languages do not require deep knowledge of hardware or machine
architecture. A programmer can write efficient programs without an in-depth knowledge
of hardware. The programmer can concentrate on solving the problem rather than
concerning the human machine interaction.
Machine
More Programmers:
Programming in low-level language is very difficult. But high-level languages
are easy to learn. It encourages more people to learn these languages. So many
programmers of high-level languages are available.
Shorter Programs: Pr ograms written in high-level languages
are shorter than low-level languages. One instruction of high-level languages
is equivalent to many instructions of low-level language.
What are the common high level languages?
The following are the high level languages:
COBOL: stands for
COmmon Business Oriented Language; it is specially designed for business
applications.
BASIC: stands for
Beginner All Purpose Symbolic Instruction Code. It was used mainly by students
to use the computer for solving simple problems.
FORTRAN: stands for
FORmula TRANslation. It has very powerful mathematical capabilities.
Pascal: it is used for
both sciencetific and business applications.
Java: it provide
strong feature for network programming.
C/C++: it is used to
write system software and application software.
What are the
differences between assembly and high level languages?
The main difference between assembly and high-level
languages are as follows:
Assembly Language
Assembly
languages are difficult to learn.
Assembly
languages are far from human languages.
Programs
in assembly languages are fast in execution.
Programs
in assembly languages are difficult to modify.
Assembly
languages provide facility to write programs at hardware level.
Knowledge
of hardware is required to write any programs.
Assembly
languages are normally used to write system software.
High-Level Language
High-level
languages are easy to learn.
High-level
languages are near to human languages.
Programs
in high-level languages are slow in execution.
Programs
is high-level languages are easy to modify.
High-level
languages do not provide much facility at hardware level.
Knowledge
of hardware is not required to write any programs.
High-level
languages are normally used to write application software.
What are differences between Low-Level and High-Level Programming
Language.
The main differences between low-level and
high-level languages are as follows:
High Level Language
High-level
languages are easy to learn.
High-level
languages are near to human languages.
Programs
in high-level languages are slow in execution.
Programs
is high-level languages are easy to modify.
High-level
languages do not provide much facility at hardware level.
Deep
knowledge of hardware is not required to write any programs.
High-level
languages are normally used to write application programs.
Low Level Language
Low-level
languages are difficult to learn.
Low-level
languages are far from human languages.
Programs
in low-level languages are fast in execution.
Programs
in low-level languages are difficult to modify.
Low-level
languages provide facility to write programs at hardware level.
Deep
knowledge of hardware is required to write any programs.
Low-level
languages are normally used to write hardware programs.
What is structured programming language?
In
structured programming languages, the entire logic of the program is divided
into number of smaller modules or function. Each module is a piece of code that
implements a different functionality. The main module calls other modules when
they are needed execute. It is a modular method of written programs. It is an
easy and simple technique to write program. The programs written in these
languages are easy to understand, modify and debug. There is also less
possibility of errors in the programs.
What is Unstructured Programming Language?
In
unstructured programming languages, the entire logic of the program is
implemented in a single module of function. The programs written in these
languages are error prone, difficult to understand, modify and debug.
What are the language processors/language translators?
Computer understands only machine language. A
program written in high-level or assembly language cannot be run on a computer
directly. It must be converted into machine language before execution. Language
processor or translator is software that converts these programs into machine
language. Every computer language has its own translator. It is a special type
of the software use for converting the software from one language to another
language. All the computer software is written in a special type of computer
software called the programming languages. There are three types of the
processors or translators:
Assembler
Interpreter
Compiler
What is assembler?
A program that translates assembly language
instructions into machine language instructions is called assembler. Assembly
language is translated in to machine language by a piece of software is called
assembler.
What is interpreter?
An interpreter is a program that converts one
statement of a program into machine at one time. It executes a statement before
translating the next statement of source program. If there is an error in the
statement, interpreter stops working and display an error message. The
advantage of interpreter over compiler is that an error is found immediately.
So the programmer can correct errors during program development. The
disadvantage of interpreter is that it is not very efficient. The interpreter
does not produce an object program. It must convert the program each time it is
executed. So we can say that interpreter can check the program line by line.
Java, Basic and Visual basic uses interpreter.
What is compiler?
A compiler is a program that converts the
instruction of a high-level language into machine language as a whole. A
program written in high-level language is called source program. The compiler
converts the source program into machine code. The machine code program is
known as object program. The object program can executed many times.
The compiler checks each statement in the source
program and generates machine instructions. Compiler also checks syntax errors
in program. A source program containing an error cannot be compiled. A compiler
can translate the programs of only those languages for which it is written. For
example, C compiler can translate only those programs that are written in C
language. Compiler can first check the entire program if there are some errors
in the whole program than it can show all the possible errors in the program.
It means compiler can check the program at whole. C, C++, COBOL and FORTRAN are
uses interpreter.
What is a linker?
Linker is a program that combines the object
program with additional library files is known as linker. It is a part of
compiler. It combines object program and library files and saves the final
machine language program as executable file. The extensive of executable files
is .exe.
What are the differences between compiler and interpreter?
The main differences between compiler and
interpreter are as follows:
Compiler
Compiler
converts a program into machine code as whole.
Compiler
create object code file.
Compiler
converts high-level program that can be executed many times.
Program
is execution is fast.
Compiler
display syntax error after compiling the whole program.
Interpreter
Interpreter
converts a program into machine code statement by statement.
Interpreter
does not create object code file.
Interpreter
converts high-level program each time it is executed.
Program
execution is slow.
Interpreter
displays the syntax error on each statement of program.
What is source
code?
Source code is a computer program written in a
high-level programming language like C, C++, Visual Basic or Java. Computer
cannot understand the statements of high-level language. The source code cannot
be executed by directly. It is converted into machine code and then executed.
What is
object code?
An object code is the program that is translated by
a language processor. It is also called machine code. Computer understands
object code directly.
What is
error? Also define its types.
An error is incorrectly written code, usually
intentional there are three types of errors.
Syntax
Errors
Logical
Errors
Run-Time
Errors
What is syntax error?
A collection of rules for writing program in a
programming language is called as syntax. Syntax error is a type of error that
occurs when an invalid statement is written in program. Syntax means any
spelling error or any typing error. Because programmer can mention wrong
spelling for the same code so it calls syntax error. Syntax errors are detected
by compiler. A program containing syntax error cannot be compiled successfully.
There can be many causes of syntax errors. Some important causes are as
follows:
The
statement terminator is missing at the end of statement.
A
variable is used without declaration.
Any of
the delimiters is missing.
Example: Typing print instead of printf is an example of
syntax error.
What is logical error?
A type of error that occurs due to poor logic of
the programmer is called as logical error. A logical error occurs when the
program follows a faulty algorithm. A statement with logical error may produce
unexpected and wrong result. If programmer make any program and then compile
them if there are not any error in the program it can run correct without any
error but the result can not show’s correctly according to programmer desire
then it calls logical error.
Example: If a programmer writes a wrong formula to
calculate the result or if a programmer use wrong loop condition or if a
programmer use wrong if condition, these are the examples of logical errors.
What is run
time error?
A type of error that occurs during the execution of
program is called run-time error. It is caused when a statement directs the
computer to execute an illegal operation such as dividing a number by zero. The
run-time errors are detected and displayed by the computer during execution.
Run-time errors are normally caused due to wrong input from the user. The
computer stops executing the program and displays error message if a runtime
error occurs.
Example: The user may ask the program to open a file that
does not exist. Similarly or the user may enter wrong type of data are the
examples of run-time errors.
What is the most difficult error?
The most difficult type of error is logical error
for the following reasons:
It cannot
detect by the compiler.
It does
not crash the program. That is why it is difficult to detect.
The user
needs to review the whole program to find out logical error(s).
It may
take a lot of time for detecting logical error.
What is bug?
A small programming error is called bug. A computer
bug is an error, fault, flaw, mistake or failure in a computer program that
prevents (stop) it from working correctly or produces an incorrect result. Bugs
arise from mistakes and errors made by programmer.
What is debugging?
Debugging is a methodical (logical) process of
finding and reducing the number of bugs. The process of finding and removing
bugs is called debugging.
What are the
testing and debugging in programming languages?
When any software company completes any software,
after completion of the same testing department can check all the software
according to the user requirements to make software free of errors. For this
purposes he can check/test all the software thoroughly, separately all modules
of the software, and if found any error in the software then correct them.
Phase in which team checks software called Testing and the phase where a team
correct error is called Debugging. So this all procedure called testing and
debugging.
What is C
language?
C is a popular high-level programming language. It
was developed at AT&T’s Bell Laboratory of USA in 1972 and it was designed
and written by a man named Dennis Ritchie. C was invented by Dennis Ritchie of
AT&T Bell Laboratories to provide a high-level language, in which the UNIX
operating system could be programmed. It is now widely used for many other
applications as well. C is especially popular with systems programmers because
it allows programs to be expressed simply and concisely. The definitive work
describing C is the programming Language by Kernighan and Ritchie (1978). Bolon
(1986), Gemani (1984), Hancock and Krieger (1986), Harbison and Steele (1984),
and numerous others have also written books about C. C is a high level language
(C is often called a "Middle Level" programming language) created by
Dennis Ritchie at the AT&T’s Bell Telephone Laboratories of USA in 1972.
The language was created for a specific purpose: to design the UNIX operating
system (which is used on many computers). Because C is such a powerful and
flexible language, its use quickly spread beyond Bell Labs. Programmers
everywhere began using it to write all sorts of programs. Soon, however,
different organizations began utilizing their own versions of C, and subtle
differences between implementations started to cause programmers headaches. In
response to this problem, the American National Standards Institute (ANSI)
formed a committee in 1983 to establish a standard definition of C, which
became known as ANSI Standard C. With few exceptions, every modern C compiler
has the ability to adhere to this standard.
Define brief
history of C language.
In 1960’s hundreds of languages had come into
existence, almost each for a specific purpose. For example: COBOL was being
used for commercial applications, FORTRAN for engineering and Scientific
Applications and so on. At this stage people started thinking that instead of
learning and using so many languages, each for a different purpose, why not use
only one language, which can program all possible applications. Therefore, an
international committee was set up to develop such a language. This committee
came out with a language called ALGOL in 1960. However, ALGOL 60 never really
becomes popular because it seemed too abstract, too general. To reduce this
abstractness and generality, a new language called Common Programming Language
(CPL) was developed at Cambridge
University Cambridge
University
|
Year
|
Language Development
|
|
1960
|
ALGOL 60
|
|
1963
|
CPL
|
|
1967
|
BCPL
|
|
1970
|
B
|
|
1972
|
C
|
Short history in points
The milestones in C's development as a language are
listed below:
UNIX
developed in 1969: DEC PDP-7 Assembly Language
BCPL: a
user friendly OS providing powerful development tools developed from BCPL.
Assembler tedious long and error prone.
A new
language called B a second attempt in 1970.
A totally
new language C a successor to B in 1972.
By 1973
UNIX OS almost totally written in C.
Where C stands for?
As we know all the programming language can be
divided in to two categories.
Low Level
Language (Machine Oriented Language)
High
Level Language (Problem Oriented Language)
C stand in between these two categories that’s why
it is often called a middle level language, since it was designed to have both
is relatively good programming efficiency (as compared to machine oriented
language) and relatively good machine efficiency (as compared to problem
oriented language).
What are the
characteristics/advantages of the C language?
Some important advantages of C language are as
follows:
Convenient Language
C is very convenient language. It provides many facilities
in easier way that are difficult to use in low-level languages. Programmers can
write complex programs more easily as compared to low-level languages.
Well-Structured Language
C is a well-structured language. Its syntax is very
easy to understand. The programs written in C language is easy to maintain and
modify.
Machine Independence
C language provides machines independence. It means
that the programs written in C language can be executed on different types of
computers. For example, a program written in C can be executed on Intel
processors and Motorola processors with a little modification. That is why it
is preferable to write program in C rather then machine language.
Modularity
C language provides the facility of modular
programming. It means that you can divide your program into small modules.
These modules can be developed and compiled independent.
Case Sensitivity
C is a case sensitive language. It means that it
can differentiate uppercase and lowercase words. All keywords are written in
lowercase. This feature makes it easier to maintain the source code.
Hardware Control
C language provides close control on hardware. You
can write efficient programs to control hardware components of computer system.
Small Language
C is a small language. It has a small number of
keywords and programming controls. But still it is every powerful for
developing different types of programs.
Fast Code Generation
The compilers of C language generate very fast
code. The code executes very efficiently. So the programs take less time to
execute.
Some more points on Characteristics of C
C is case
sensitive language
C is a
structured language
C is a
language of few words (Small size)
C has
high-level constructs
C can
also handle low-level activities
C can
produce efficient programs
C can be
compiled on a variety of computers
C can
extensive use of function calls
C
language program has a extension .c
C
statements are terminated with semicolon
What are the
features of the C Language?
Ability
to write very concise source codes in spite of having a large number of
operators.
It has a
small instruction set
It has
library functions that enhance the basic instruction.
The
features and capabilities can be easily extended b the users as it encourages
users to write additional library functions
C
Compliers are compact and generate smaller and highly efficient object code
compared to other high level languages.
C
Programs are highly portable as its library set avoids all to computer
dependent features.
C
Compliers are compact and generate smaller and highly efficient object code
compared to other high level languages.
C
Programs are highly portable as its library set avoids all to computer
dependent features.
What are the
program characteristics of c language?
The program characteristics are as follows:
Integrity
Clarity
Simplicity
Efficiency
Modularity
Generality
What are C character
sets?
Uppercase
A - Z
Lowercase
a - z
Digits 0
– 9
Special
characters
These are used as building blocks to form basic
program elements.
What is the Turbo C++ IDE?
The compiler used for C language is Turbo C++. It
is the implementation for Borland International for C language. Turbo C also
provides a complete Integrated Development Environment (IDE) known as TC
editor. It is used to create, edit and save programs. It also provides a
powerful debugger. The debugger helps users in detecting and removing errors in
programs. The process of writing programs in Turbo C editor is very easy. The
user can type TC on DOS prompt or double click TC shortcut to start IDE. The
menu bar of IDE contains menus to create, edit, compile, execute and debug a C program.
The user can open a menu by clicking on it with the mouse. The user can also press
a combination of ALT key and the first highlighted character of the name of
menu. For example ALT+F is used to open File menu.
What are the debugging features of Turbo C++?
Turbo C++ provides many useful debugging features.
The debugging features of Turbo C++ are available in Debug menu. Some important
debugging features of Turbo C++
are as follows:
Single Stepping: A program may not execute
even if it has been compiled successfully. The debugger provides the facility
to find errors by executing one line of a program at one time. It enables the
programmer to detect the exact place of error. The following procedure is used
to execute one step at a time with single stepping Select Run> Trace into or
press F7.
Watches: The watch or watch expression is used to check the
value of a variable as the program executes. It indicates how the values of
variables change during program execution. It is normally used in combination
with single stepping. The following procedure is sued to use watch or watch
expression:
Place the
cursor on the variable whose value is to be checked.
Select
Debug > Watches. A submenu will appear.
Select
Add Watch from the submenu. OR press CTRL+F7. A dialog box will appear.
The
selected variable will appear in Watch expression field.
Click OK
OR press Enter. A new window will appear indicating that the selected symbol is
undefined.
Select
Run > Trace into OR press F7 to execute single stepping. The value of the
selected variable will appear in Watch window.
Breakpoints: A breakpoint is used to mark a part of program
where program execution will stop. The program executes all statements up to
the breakpoint and then stops. The user can check the values of a variable at
this point by using Watch window by single stepping remaining part of the
program. The following procedure is used to insert a breakpoint in the program:
Place the
cursor on the line on which the breakpoint is to be inserted.
Select
Debug > Toggle breakpoint or press CTRE+F8. The breakpoint will be inserted
and the line will be highlighted.
Evaluate/Modify Window: The
evaluate/modify window is used to change the value of variable during program
execution. It can be useful if the user is single stepping the program and
wants to change the value of a certain variable. The following procedure is used
to use evaluate/modify window:
Select Debug
> Evaluate/Modify. A new window will appear with three fields.
Enter the
name of the variable whose value is to be modified in Expression field.
Enter the
new value for the variable in New Value field. The value of the third field Result
will also change automatically.
How to Write, Edit, Compile, Link and Run the C Program?
We use Turbo IDE that provides the central location
where the entire C program that can be written, compile, link and run.
Following steps are required for working with Turbo C++ IDE.
Step 1: Select the icon/shortcut TC.EXE from the BIN
folder present in the TC.
C: – TC – BIN – TC.EXE
This action will open the Turbo C++ IDE, where we
can perform all the relevant activities associated with the C program. After
properly opening the Turbo C++ IDE, a program with blue color will be appeared
on the screen. It is the place where we do our programming work.
Step2: Now write the following program in Turbo C++ IDE.
|
Simple C Program
|
|
#include<stdio.h>
#include<conio.h>
void main(void)
{
clrscr();
printf("I am Javed Iqbal.");
getch();
}
|
|
Output
|
|
I am Javed Iqbal.
|
Step 3: Now save the file with the name javed.c by
pressing F2 or by selecting the Save option from the File Menu.
Step 4: Now compile the file by pressing the Alt + F9 or
by selecting the Compile option of the compile menu (after the successful
compilation of .c and object file .obj will be generated).
Step 5: Now link the file by selecting the link option of
the Compile menu. After linking the file the .exe will be generated.
Step 6: Instead of Using the Option 4 and 5 directly press
F9 or use the Make option of the of the Compiler menu, that which the program
is compile and link with the single command.
Step 7: For running the program press Ctrl+F9 or select
the Run option from the Run menu. After selecting this option the Turbo C++ IDE
will run the program but before running the IDE compile and link the file
automatically so instead of using the options 4 to 6 simply press the Run or
Ctrl + F9 by which the compile, linking and running process will be perform in
a single tern.
Step 8: If we don’t use getch(); function so we cannot
view the output directly. Without using getch(); function we displaying the
output by pressing the Alt+F5.
Step 9: Press Alt+F3 or select the Close option from the
Window menu, to close the active file.
Step 10: Press Alt + X or select the Quit option from the
File menu to exit from the Turbo C++ IDE.
What is the basic
structure of the C program?
The format of writing C program is called its structure.
The basic structure of a C program is very flexible. It increases the power of
language. It consists of the following:
Preprocessor
Directive (#)
Main()
function
Body of
the program (C Statements)
In the above program
First line
is preprocessor directive to include a header file stdio.h. The preprocessor
directives are the commands that give instructions to C, preprocessor.
Preprocessor is a program that modifies C source program before compilation.
The preprocessor directives start with hash symbol #.
Second
line is also preprocessor directive to include a header file conio.h.
The third
line is main function. The word void before the function main() means that this
function does not return a value and the second void inside the bracket means
it does not have any argument. The main() function is the place where execution
of a C program starts. When the program is executed, the control enters main()
function and starts executing its statements.
The
statements of the program are written in curly braces. The curly brace { is
called opening brace and } is called closing brace. The braces are also known
as delimiters. These statements are collectively known as the body of the
program.
Every
statement in C program is terminated with a semicolon (;). The compiler
generates an error if any statement is not terminated by semi colon (;).
What is the #include<stdio.h>?
The # sign indicates that this is an instruction
for the C compiler and includes information about how to use the functions from
the <stdio.h> stand for Standard Device Input/Output header file. Usually
the standard input device is your keyboard and the standard output device a
terminal which is displayed on your monitor. One item included in this header
is a declaration of the function printf(). This library is very widely used.
What is the #include <conio.h>?
This line tells C to include information about how
to use the functions from the Common Input Output library.
What is void main()?
main() is a program building block called function.
C programs contain one or more functions, exactly one of which must be main().
The keyword void to the left of the main indicated that main can not return any
value. The parentheses after main indicates that main is a program building
block called function. { the left braces begin the body of every of every
function and a corresponding right brace } must means end the body of each
function.
What is clrscr();?
It is a built in function for clear screen and as ;
(semicolon) at the end of line its means that the statement end with ; all the
statements in C are terminated ; (semicolon) called terminator.
What is printf(“Hello! Students.”);?
It is also a built in function of C to interact
compiler for print message in console output screen, which are mention with
parentheses and double quote.
What is getch();?
It is also a built in function, this function can
get any character from user on run time, and mostly this function is used for
stop any program on any specific location when user can enter any key then program
goes on.
What is
Preprocessor?
The preprocessor is used to modify your program
according to the preprocessor directives in your source code. Preprocessor
directives (such as #define) give the preprocessor specific instructions on how
to modify your source code. The preprocessor reads in all of your include files
and the source code you are compiling and creates a preprocessed version of
your source code. This preprocessed version has all of its macros and constant
symbols replaced by their corresponding code and value assignments. If your
source code contains any conditional preprocessor directives (such as #if), the
preprocessor evaluates the condition and modifies your source code accordingly.
The preprocessor contains many features that are powerful to use such as
creating macros, performing conditional compilation, inserting predefined
environment variables into your code and turning compiler features on and off.
For the professional programmer in-depth knowledge of the features of the
preprocessor can be one of the keys to creating fast efficient programs.
What are the preprocessor directives?
The preprocessor directives are commands that give
instructions to C preprocessor. It is also known as compiler directive. The
preprocessor is a, program that modifies C source program before compilation.
The preprocessor directives start with hash symbol #. These directives are
written at the start of program. Many necessary actions such as input and
output are not defined directly in C programs. These actions are defined in the
form of function. These functions are stored in C libraries. Each library has a
standard header file. A header file always has .h extension. The file stdio.h
is a header file. It contains definition of standard input/output functions.
What are the types of preprocessor directives?
Two types of preprocessor directives used in C
language are as follows:
Include
preprocessor directive
Define
preprocessor directive
What is the include preprocessor directive?
The "include" preprocessor directive
enables a program to access a library. It allows the preprocessor to insert
definitions from a standard header file into C program before compilation. It
is used to include header files in the program.
Syntax: The syntax of using this directive is as follows:
#include <standard header file>.
Example #include <stdio.h> , #include <math.h>
The above statement tells preprocessor to include
the file stdio.h in the source program before compiling it. The include
directive tells the compiler where to find the meanings of standard identifiers
such as printf. The meanings are described in standard header files. The header
file stdio.h contains information about standard input and output functions
such as scanf and printf. The math.h contains information about common
mathematical functions.
What is the define preprocessor directive?
The define preprocessor directive is used to define
constant macro.
Syntax: The syntax of using this directive is as follows:
#define Macro _Name
Expression
The expression can be a constant, arithmetic
expression or a string. C preprocessor replaces each occurrence of the
identifier Macro Name with the value of the expression before compilation. The
expression or the identifier Macro Name cannot be changed during program execution.
Example: #define a 10
The above line defines an identifier a that represents the value 10.
What is a
Header File?
Header files contain declarations to functions and
variables and have a .h extension. Examples of header files include stdio.h, string.h
and strlib.h. Header files have the extension .h and the full filename follows
from the #include directive. They contain declarations to certain functions
that you may or may not have used in your program. For example, the stdio.h
file is required if you have used functions like printf and scanf in your
program. There are two ways to include a header file: #include
"stdio.h" and #include <stdio.h>. If you use the double quote
marks it means that the directory you're currently in, will be searched for
first for the header file before any other directories are searched. If you use
the angled brackets directories other than the one you're currently in will be
searched for the header file. Usually this will be the default directory for
header files specified in your compiler so you'll probably be using square
brackets all the time.
#include<stdio.h> The # sign
indicates that this is an instruction for the C compiler and includes
information about how to use the functions from the <stdio.h> stand for
Standard Device Input/Output header file. Usually the standard input device is
your keyboard and the standard output device a terminal which is displayed on
your monitor. One item included in this header is a declaration of the function
printf(). This library is very widely used.
#include <conio.h> This line tells
C to include information about how to use the functions from the Common Input
Output library.
What is main
function?
A function is like a subroutine where a group of
instructions are evaluated when the function is called. All C programs must
have a main function. You can only have one but you can place it anywhere
within the code. The program always starts with the main function and ends when
the end of main is reached. Functions RETURN a value too in other words passes
back a value to the program. If a function returns nothing its return type is
of type void i.e. nothing is returned. The main function is special as it
returns an integer by default which is why you'll see me write return 0; at the
end of the program. Zero is usually returned to indicate error-free function
termination. Another way to terminate a program is to use the exit function,
there's an example.
#include <stdio.h>
int main()
{
clrscr();
printf("Hello
Javed!\n");
return 0;
}
What is a
local block?
A local block is any portion of a C program that is
enclosed by the left brace ({) and the right brace (}). A C function contains
left and right braces and therefore anything between the two braces is
contained in a local block. An if statement or a switch statement can also
contain braces so the portion of code between these two braces would be
considered a local block.
What are
memory models?
The compiler uses a memory model to determine how
much memory is allocated to the program. The PC divides memory into blocks
called segments of size 64 KB. Usually, program uses one segment for code and a
second segment for data. A memory model defines the number of segments the
compiler can use for each. It is important to know which memory model can be
used for a program. If we use wrong memory model, the program might not have
enough memory to execute. The problem can be solved using larger memory model.
However, larger the memory model, slower is your program execution. So we must
choose the smallest memory model that satisfies our program needs. Most of the
compilers support memory models like tiny, small, medium, compact, large and
huge.
What is the
purpose of the statement #include<stdio.h> in a C program?
The purpose of #include<stdio.h> is include
usually the standard device input/output is your keyboard and the standard
output device a terminal which is displayed on your monitor. That item included
in this header is a declaration of the function printf(), scanf() etc. almost any
program needs to perform input/output operations. Therefore, most of the C
program must be preceded by this instruction. This library is very widely used.
The # sign indicates that this is an instruction for the C compiler and
includes information about how to use the functions from the <stdio.h>
stand for Standard Device Input/Output header file. Assembly language is
translated by a translator program called as Assembler. High-level language is
translated by translators program "Compiler or Interpreter".
What is a
function?
A function is a named block of code that performs
some action. The statements written in a function are executed when it is
called by its name. Each function has a unique name. A function is a piece of
code i.e. designed to perform a specific task. It is a complete and independent
program. It is executed by the main function or any other function of the
program. Functions are the building blocks of C programs.
What is
main() function?
The main() function is the place where execution of
a C program starts. When the program is executed, the control enters main()
function and starts executing its statements.
Write a
program that will print the message "I Love Computers" and compile
and run it on the computer.
|
Simple C Program
|
|
#include<stdio.h>
#include<conio.h>
void main(void)
{
clrscr();
printf("I Love Computers");
getch();
}
|
|
Output
|
|
I Love Computers
|
After writing the above program we will compile it
with the help of pressing Alt+F9 or by selecting the compile option from the
compile menu (after the successful compilation of .c and object file .obj will
be generated). For running the program we will press Ctrl+F9 or select Run
option from the run menu. The effect is that the string “I Love Computers” is
printed on the screen when the program runs.
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