Lecture Notes: Control Statements in C

Introduction

• Focus on iterative and loop control statements in C.
• Types of loops: while, do-while, for.
• Special control statements: goto, break, continue.

Iteration and Looping

• Iterative execution of statements is called looping.
• A loop executes a statement or a block repeatedly until a condition is met.
• Example: Convert Fahrenheit to Celsius for 10 values using a loop instead of running a program 10 times.

Types of Loops in C

Pretest Loops

• While and For are pretest loops.
  • Condition is checked before each iteration.
  • If true, loop executes; if false, it skips to the next statement.
• Example: Packing products on a conveyor belt with a pre-determined count checked before packaging.

Post-test Loops

• Do-while is a post-test loop.
  • Executes code once before condition is checked.
  • If true, loop continues; if false, it stops.
• Example: Packing products on a conveyor with a check at the exit for the count.

Loop Process Steps

1. Initialization: Assign a value to the counter variable.
2. Condition Evaluation: Decide to continue or exit based on a condition.
3. Increment/Decrement: Update the counter variable after each loop iteration.

Types of Loop Control

• Event-Controlled Loop: Iteration based on an event occurrence.
• Counter-Controlled Loop: Iteration based on a predetermined count.

Detailed Loop Explanations

While Loop

• Pretest Loop
• Test condition controls loop execution.
• Depends on whether test condition is true or false.
• Example: Counting products on a conveyor belt.

Do-While Loop

• Similar to while but test condition is checked after execution.
• Guarantees execution at least once.
• Example: Similar conveyor belt example with a condition check at the end.

For Loop

• Similar to While, written differently.
• Includes initialization, condition, and increment in one statement.
• Called a definite loop due to a known number of iterations.
• Example: Conveyor belt with a set number of products.

Special Control Statements

Break

• Used to stop execution immediately within a loop.
• Transfers control to statements after the loop.
• Example: Terminate loop when user input reaches a specified value.

Continue

• Stops current iteration and moves to the next.
• Used within loops to skip certain conditions.
• Example: Print numbers 1 to 5 excluding 3.

Goto

• Used for jumps within a function.
• Transfers control to a labeled statement.
• Example: Repeatedly prompt user for input until a stop condition.

Summary

• Reviewed types of loops: pretest (while, for) and post-test (do-while).
• Loops can be programmed as event or counter-controlled.
• Discussed special statements break, continue, and goto for control flow.
• Emphasized the structured use of loops and limited use of goto.