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COMPUTER PROGRAMMING I
(TA C162)
Lecture 26 – Basics of C Programming
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Today’s Agenda
Structure of a C program
2
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Our Text Book
Saturday, March 20, 2010 Biju K Raveendran@BITS Pilani. 3
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About C General purpose structured programming
language
Characterized b the abilit to write ver
concise source program
Comparatively small instruction set
Programs are highly portable
4
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Structure of a C Language Program/* Program to compute …………………………. */
#include<stdio.h>
/*Library files inclusion *//* Global variable declaration …………………*/
{
/* local variable declarations */
/* initialization */
/* statements */
re urn ;}
5
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Structure of a C Program very program cons s s o one or more mo u es ca efunctions.
One of the functions must be called main.
Execution will always begin by main.
Each compound statement is enclosed within a pair ofbraces
{
Statement1;
Statement2;………
}
Each statement must end with a semicolon (;)
Anything within /* */ treated as comments Comments may appear anywhere within program
6
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Our first C Program/* Converts the distance from miles to kilometer
*/
#include <stdio.h>
_ _ .
int main(void){
double miles, kms;
/*get the distance in miles*/
printf(“ Enter the distance in miles : ” );
scanf(“ %lf” ,&miles );conver e s ance o ome ers
kms=KMS_PER_MILE * miles;
/* Display the result in kilometers*/
“ ” ,
return(0);
}
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Our first C Program/* Converts the distance from miles to kilometer
*/
#include <stdio.h>
Comments
_ _ .
int main(void){
double miles, kms;
ny ng e ween
is interpreted ascomment and is
/*get the distance in miles*/
printf(“ Enter the distance in miles : ” );
scanf(“ %lf” ,&miles );
compiler
conver e s ance o ome ers
kms=KMS_PER_MILE * miles;
/* Display the result in kilometers*/
“ ”
escr es e ey
operations of the
program ,
return(0);
} Note: Placing one
comment inside the
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Comments in C Used for improving readability of the program
compiler
/* line(s) of text ……. */
All the text between /* and */ are commented
// One line of text
Commented the text till the end of that line
Saturday, March 20, 2010 Biju K Raveendran@BITS Pilani. 9
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Our first C Program/* Converts the distance from miles to kilometer
*/
#include <stdio.h>
Preprocessor Directives:
Modifies the C program
before the com ilation _ _ .
int main(void){
double miles, kms;
begin #include directive gives a
ro ram access to a librar /*get the distance in miles*/
printf(“ Enter the distance in miles : ” );
scanf(“ %lf” ,&miles );
stdio.h is a standard Cconver e s ance o ome ers
kms=KMS_PER_MILE * miles;
/* Display the result in kilometers*/
“ ”
In this program, it supports
printf, scanf functions
,
return(0);
} Each l ibrary has a standard
header fi le whose name
ends with .h
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Our first C Program/* Converts the distance from miles to kilometer
*/
#include <stdio.h>
Function Main:
_ _ .
int main(void){
double miles, kms;
function where theexecution begins
/*get the distance in miles*/
printf(“ Enter the distance in miles : ” );
scanf(“ %lf” ,&miles );
Every C program has a
main functionconver e s ance o ome ers
kms=KMS_PER_MILE * miles;
/* Display the result in kilometers*/
“ ”
The remaining lines
(function body) of the,
return(0);
}
within the braces { }
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Our first C Program/* Converts the distance from miles to kilometer
*/
#include <stdio.h>
Function Main:
_ _ .
int main(void){
double miles, kms;
{function body
/*get the distance in miles*/
printf(“ Enter the distance in miles : ” );
scanf(“ %lf” ,&miles );
}
Function body has 2conver e s ance o ome ers
kms=KMS_PER_MILE * miles;
/* Display the result in kilometers*/
“ ”
parts
Declarations
Executable statements ,
return(0);
}
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Tell the compiler the names of memory cells in aprogram
Example: miles, kms
Programmer uses the data requirement analysis
Executable statements
language instructions and executed by the computer
Saturday, March 20, 2010 Biju K Raveendran@BITS Pilani. 14
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Our first C Program/* Converts the distance from miles to kilometer
*/
#include <stdio.h>
int main(void)
Returns an integer to the
o eratin s stem after _ _ .
int main(void){
double miles, kms;
completing the main
function
Receives no data from the/*get the distance in miles*/
printf(“ Enter the distance in miles : ” );
scanf(“ %lf” ,&miles );
operating system before
it begins execution
conver e s ance o ome ers
kms=KMS_PER_MILE * miles;
/* Display the result in kilometers*/
“ ”
return(0) :
Returns the control from,
return(0);
}
operating system
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