Control Structures

UNIT II

Control Structures

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• There are four types of control structures /statements
• 1. Sequence statements
• 2. Selection also called as decision making statements
• 3. Iteration statements
• 4 Jump statements

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Control Structures

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• 1. Sequential Control

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• Default flow: statements are executed one after another in order.

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Sequential Control

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• #include <stdio.h>
• int main() {
• int a = 10, b = 20, sum;
• sum = a + b; // executed first
• printf("%d\n", sum); // executed next
• return 0;
• }

Sequential Control

Statement 1

Statement 2

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Statement 3

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Conditional Control (Selection Control or Decision Control) :-

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• In conditional control , the execution of statements depends upon the condition-test. If the condition evaluates to true, then a set of statements is executed otherwise another set of statements is followed.
• This control is also called Decision Control because it helps in making decision about which set of statements is to be executed.

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• Decision control structure in C can be implemented by using:-
• 1. If statement
• 2. If-else statement
• 3. Nested if else statement
• 4. else-if ladder
• 5. switch case

if statement:-

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• This is the most simple form of decision control statement.
• In this form, a set of statements are executed only if the condition given with if evaluates to true.
• Its general syntax and flow chart is as under:
• - if(condition)
• {
• Statements ;
• }

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1. If Statement Flow chart

2. The if-else Statement:

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• In the if–else statement, if the expression/condition is true, the body of the if statement is executed; otherwise, the body of the else statement is executed.

2. The if-else Statement: Syntax

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• Syntax:
• if(condition)
• {
• execute the statement1;
• }
• else
• {
• execute the statement2;
• }

2. The if-else Statement: Syntax

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•  condition returns true then the statements inside the body of “if” are executed and the statements inside body of “else” are skipped.
• �If condition returns false then the statements inside the body of “if” are skipped and the statements in “else” are executed

2. The if-else Statement: Flow Chart

3. Nested if else statement�

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• When an if else statement is present inside the body of another “if” or “else” then this is called nested if else.

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Nested if else statement Syntax

• if (condition1) {
• // code if condition1 is true
• if (condition2) {
• // code if BOTH condition1 and condition2 are true
• }
• else {
• // code if condition1 is true but condition2 is false
• }
• }
• else {
• // code if condition1 is false
• }

3.Nested if else statement: Flow chart

Nested if else statement Flow Chart�

�If else Ladder�

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• An if else ladder is a programming construct used for decision-making.
• It consists of a series of if else statements chained together, forming a ladder-like structure.
• Each if else statement is evaluated sequentially until a condition is found to be true, and the corresponding block of code is executed.
• If none of the conditions are true, the code within the else block (if present) is executed.

Basic Syntax of If else Ladder:�

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• if (condition1) {� // Code to be executed if condition1 is true�} else if (condition2) {� // Code to be executed if condition2 is true�} else if (condition3) {� // Code to be executed if condition3 is true�} else {� // Code to be executed if none of the conditions are true�}
• �

switch case

• The switch statement in C is a multi-way decision control structure that allows a program to execute different blocks of code based on the value of a single expression. 
• It provides an alternative to using a series of if-else if statements when dealing with multiple specific conditions. 

switch case syntax

• switch (expression) {�case constant1:�// Code to execute if expression matches constant1�break;�case constant2:�// Code to execute if expression matches constant2�break;�// ... more case statements�default:�// Code to execute if no case matches�}