Fundamentals of Programming Lecture 6 Hamed Rasifard 1 Outline - - PowerPoint PPT Presentation

Fundamentals of Programming

Lecture 6 Hamed Rasifard

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Outline

• Expressions
• Assignment Operators
• Increment and Decrement Operators
• if Selection Structure
• if/else Selection Structure

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Expressions

• Formulas that show how to compute a value
• The simplest expressions are variables and

constants

• More complicated expressions apply operators

and operands

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C’s Operator

• Arithmetic operators
• Relational operators
• Logical Operators

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Assignment Operators

• C’s Assignments operator:

Simple Assignment Compound Assignment

• lvalue: represent an object stored in memory
• Assignment operator requires a lvalue as its

left operator

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Simple assignments

• Simple assignment operator (=) is used to store

the value of a expression in a variable

int i,j,k; float f; i = 7; j = i * 10; k = 2 * ( j = i); k = j = i = 9; f = i = 77.7f;

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Compound Assignment

• It is common to use old value of a variable to

compute new value of that variable

• Compound assignments operator let us to

shorten this kind of statements

• Compound operators: +=, -=, *=, /=, %=

simple assignment: i = i + 2; compound assignment: i += 2;

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Increment and Decrement Operators

• Two most common operation on a variable are

incrementing and decrementing

• simple and compound assignments could be

used for incrementing and decrementing a variable

• C’s increment (++) and decrement (--)

assignments allow us to shorten these expression even further

i = i + 1; i++; or ++i; i = i - 1; i--; or --i;

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True or False

• The value of a expression is true or false
• Several of C’s statements work based on the

value of a expression

• In c, integer number 0 is interpreted as false,

and integer number 1 is interpreted as true

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if Selection Statement

• Dynamic programs need to have various output

to various situations

• if statement allows a program to choose a

particular execution path from two alternatives

• if statement decides the execution path based
• n value of an expression

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Flowcharting the Single- Selection if Statement

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if Statement Form

• Form of if Statement:
• Parentheses around the expression are

mandatory

• There is no any then
• Compound statements:

if (expression) statement if (expression) {statements}

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if/else Statement

• if/else statement let us have different actions

when expression value is true or false

• General form of if/else statement:

if (expression) {statement(s)} else {statement(s)}

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Flowcharting the Double- Selection if/else statement

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Nested if/else statements

• Test for multiple cases by placing if/else

statement inside if/else statements

if (expression) {statement(s)} else if (expression) {statement(s)} else if (expression) {statement(s)} else . . .

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Other Form of Nested if/else Statement

if (expression) {statement(s)} else if {statement(s)} else if {statement(s)} else if {statement(s)} else if {statement(s)} . . .

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Dangling else problem

• Consider following statements:
• You should enclose inner if statement in braces

if (y != 0) if (x != 0) result = x/y; else printf(“ERROR, y is equal to 0\n”);

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