Introduction to Loops, Lecture notes of Programming Languages

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LEC 10 & 11

LOOPS

• (^) A Loop executes the sequence of statements many times until the stated condition becomes false. A loop consists of two parts, a body of a loop and a control statement.
• (^) C programming has three types of loops:
• (^) for loop
• (^) while loop
• (^) do...while loop

Syntax :

variable initialization; while(condition) { statements; variable increment or decrement; }

• (^) Example: Program to print first 10 natural numbers #include<stdio.h> void main( ) { int x; x = 1; while(x <= 10) { printf("%d\t", x); /* below statement means, do x = x+1, increment x by 1*/ x++; } }

#include<stdio.h> void main () { int j = 1; while (j+=2,j<=10) { printf("%d ",j); } printf("%d",j); }

#include<stdio.h> void main () { while () { printf("hello Javatpoint"); } } Output compile time error: while loop can't be empty

do...while loop

• (^) The do..while loop is similar to the while loop with one important difference. The body of do...while loop is executed at least once. Only then, the test expression is evaluated.

• (^) The syntax of the do...while loop is: do { // statements inside the body of the loop } while (testExpression);

#include<stdio.h> #include<conio.h> int main() { int num=1; //initializing the variable //do-while loop do { printf("%d\n",2*num); num++; //incrementing operation } while(num<=10); return 0; }

#include<stdio.h> void main() { int a, i; a = 5; i = 1; do { printf("%d\t", a*i); i++; } while(i <= 10); }