08 Es26 Lab - Loops

Introduction to Loops

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Introduction to Programming

Iteration Control Structure • Doing something more than once – Do until a condition happens – Do as long as a condition happens • Parts of a Loop – Conditional (Boolean) Expression – Body of Loop • Repeat body until conditional is false

Introduction to Programming

Iteration Control Structure 3 Types: • While loop • Do-while loop • For loop

Introduction to Programming

While Loop 

Simplest loop in C

Syntax: while (cond) { [statements] }

Semantics: • Continue as long as cond is true: • When cond false, on to next statement • If cond false first time, block isn't executed

Introduction to Programming

Example 1: Using While Loop • Problem: Compute the sum of the numbers between 1 to 10, inclusive. int sum = 0, counter=1; while(counter <=10) { sum = sum + counter; counter++; } Introduction to Programming

Example 2: Using While Loop int main(void) { int number; scanf("%d",&number); while (number >= 0 ) { printf("%d\n", number *2 ); scanf("%d" , &number); } printf("done! \n"); return 0; } Introduction to Programming

Do-While Loop • Always do block at least once • Repeat as long as condition is true do{ [statements] } while (condition); • Notice the semicolon at the end • If condition is false, block done at least once Introduction to Programming

Continue and Break Statements • continue – Ignore rest of loop – Go back to top of loop • break – Ignore rest of loop – Break out of loop

Introduction to Programming

Example: Using Break count = 1; while (count<=10) { scanf("%d",&number); if (number<0) break; count = count+1; } Introduction to Programming

Example: Nested loops #include <stdio.h> int main() { int x ,y; x = 0; do{

y = 0; do{ printf("*"); y = y+1; }while (y < 5);

printf("\n"); x = x+1; }while(x <3); return 0; }

/*y++;*/

/* x++ */ Introduction to Programming

Programming Exercise (while, do-while) • Write a C program that displays at the left margin of the screen a solid triangle of asterisks whose side is an integer value given by the user. For example, if side is 3, the program displays the following patterns, one below the other. Enter number of sides: 3 * ** *** Introduction to Programming

Programming Exercise (while, do-while) • Write a C program that displays at the left margin of the screen a solid triangle of asterisks whose side is an integer value given by the user. For example, if side is 3, the program displays the following patterns, one below the other. Enter number of sides: 3 *** ** * Introduction to Programming