C Programming: Repetition and Control Statements, Slides of Computer Fundamentals

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ISE105: Computing Fundamentals

Lecture 9

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Chapter 4 – C Program Control

Outline 4.1 Introduction 4.2 The Essentials of Repetition 4.3 Counter-Controlled Repetition 4.4 The for Repetition Statement 4.5 The for Statement: Notes and Observations 4.6 Examples Using the for Statement 4.7 The switch Multiple-Selection Statement 4.8 The do…while Repetition Statement 4.9 The break and continue Statements 4.10 Logical Operators 4.11 Confusing Equality (==) and Assignment (=) Operators 4.12 Structured Programming Summary

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4.1 Introduction

• This chapter introduces
  • Additional repetition control structures
    • for
    • Do…while
  • switch multiple selection statement
  • break statement
    • Used for exiting immediately and rapidly from certain control

structures

• continue statement
  • Used for skipping the remainder of the body of a repetition

structure and proceeding with the next iteration of the loop

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4.2 The Essentials of Repetition

• Loop
  • Group of instructions computer executes repeatedly while some condition remains true
• Counter-controlled repetition
  • Definite repetition: know how many times loop will execute
  • Control variable used to count repetitions
• Sentinel-controlled repetition
  • Indefinite repetition
  • Used when number of repetitions not known
  • Sentinel value indicates "end of data"

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4.3 Essentials of Counter-Controlled Repetition

• Example:

int counter = 1; // initialization while ( counter <= 10 ) { // repetition condition printf( "%d\n", counter ); ++counter; // increment }

• The statement int counter = 1;
• Names counter
• Defines it to be an integer
• Reserves space for it in memory
• Sets it to an initial value of 1

OutlineOutline

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fig04_01.c

Program Output 1 2 3 4 5 6 7 8 9

10

OutlineOutline

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fig04_02.c

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4.4 The for Repetition Statement

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4.4 The for Repetition Statement

• For loops can usually be rewritten as while loops:

initialization;

while ( loopContinuationTest ) {

statement;

increment;

• Initialization and increment
  • Can be comma-separated lists
  • Example:

for (int i = 0, j = 0; j + i <= 10; j++, i++)

printf( "%d\n", j + i );

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4.5 The for Statement : Notes and Observations

• Arithmetic expressions
  • Initialization, loop-continuation, and increment can contain arithmetic expressions. If x equals 2 and y equals 10 for ( j = x; j <= 4 * x * y; j += y / x ) is equivalent to for ( j = 2; j <= 80; j += 5 )
• Notes about the for statement:
  • "Increment" may be negative (decrement)
  • If the loop continuation condition is initially false
    • The body of the for statement is not performed
    • Control proceeds with the next statement after the for statement
  • Control variable
    • Often printed or used inside for body, but not necessary

OutlineOutline

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fig04_05.c

Program Output Sum is 2550