Control statements and loops are fundamental programming constructs that determine how a program makes decisions and repeats tasks. They allow developers to execute specific blocks of code based on conditions and automate repetitive operations efficiently.
Learning Objectives
Use if, if-else, and nested if statements
Implement switch statements
Write for, while, and do-while loops
Use break and continue
Choose the appropriate control structure for different programming scenarios
Decision Making Using if Statement
The if statement executes a block of code only when a specified condition is true.
Example
#include <stdio.h>
int main()
{
int marks = 80;
if (marks >= 50)
{
printf("Pass");
}
return 0;
}
Output
Pass
if...else Statement
The if...else statement executes one block when the condition is true and another when it is false.
#include <stdio.h>
int main()
{
int age = 16;
if (age >= 18)
{
printf("Eligible to vote");
}
else
{
printf("Not eligible");
}
return 0;
}
switch Statement
The switch statement selects one block of code from multiple options.
#include <stdio.h>
int main()
{
int day = 3;
switch(day)
{
case 1:
printf("Monday");
break;
case 2:
printf("Tuesday");
break;
case 3:
printf("Wednesday");
break;
default:
printf("Invalid Day");
}
return 0;
}
Output
Wednesday
Arithmetic Expressions
Expressions combine variables, constants, and operators to produce a value.
Example:
int total = (20 + 10) * 2;
Understanding operator precedence ensures expressions are evaluated correctly.
Looping in C
Loops allow a block of code to execute repeatedly until a specified condition becomes false.
C provides three primary looping constructs:
for
while
do-while
for Loop
The for loop is commonly used when the number of iterations is known.
#include <stdio.h>
int main()
{
int i;
for(i = 1; i <= 5; i++)
{
printf("%d\n", i);
}
return 0;
}
Output
1
2
3
4
5
while Loop
The while loop evaluates the condition before executing the loop body.
#include <stdio.h>
int main()
{
int i = 1;
while(i <= 5)
{
printf("%d\n", i);
i++;
}
return 0;
}
do...while Loop
The do...while loop executes the loop body at least once before checking the condition.
#include <stdio.h>
int main()
{
int i = 1;
do
{
printf("%d\n", i);
i++;
} while(i <= 5);
return 0;
}
break Statement
The break statement immediately exits the loop.
for(int i=1; i<=10; i++)
{
if(i==6)
break;
printf("%d\n", i);
}
Output
1
2
3
4
5
continue Statement
The continue statement skips the current iteration and moves to the next one.
for(int i=1; i<=5; i++)
{
if(i==3)
continue;
printf("%d\n", i);
}
Output
1
2
4
5
Best Practices
Use meaningful conditions.
Avoid deeply nested if statements.
Use switch when multiple fixed options exist.
Choose the appropriate loop based on the problem.
Avoid infinite loops.
Use break and continue only when they improve readability.
Common Mistakes
Missing break statements in switch.
Incorrect loop conditions causing infinite loops.
Forgetting to increment loop variables.
Using assignment (=) instead of comparison (==) in conditions.
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