Lec4 Loops.pptnew1

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    s

    s

    CS 1001 Programming in CLecture 4

    More on Decision

    Making and Loops inC

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    Logic Operators in if

    Equal to if (x==10)

    Not equal to if (x!=10) Less than if (x10)

    Less than / equal to if (x=10)

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    Compound Operators

    Logical AND if (x==1 && y==2)

    Logical OR if (x==1 || y==2)

    Logical NOT if (!x)

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    Single and Compound Statements

    Single statements:

    if (condition)

    true_statement;

    elsefalse_statement;

    Multiple statements:

    if (condition) {

    }

    else {

    }

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    Nested If Statements

    void main(void)

    {int winner =3;

    printf(and the winner of ICC is );

    if (winner==1) printf(Pakistan);

    else if (winner==2)

    printf(England);

    else if (winner==3)

    printf(WI);

    else

    printf(Australia);

    }

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    Conditional Statement

    void main(void)

    {

    int num;

    printf("Enter a value:");

    scanf("%d", &num);

    if (num < 0)

    printf("The value is negative\n");

    else if (num == 0)

    printf("The value is zero\n");

    else

    printf("The value is positive\n");

    return 0;

    }

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    Switch Statements

    Switch statements look like thisexample:

    switch (expression) {

    value_1 : statements_1; break;

    value_2 : statements_2; break;

    ...

    value_n : statements_n; break

    default

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    switch (winner) {

    case 1 : printf(Pakistan);

    break;

    case 2 : printf(England);

    break;

    .

    value_n : statements_n; break

    default:

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    Loops

    Repeat a series of statements Not reasonable to copy statements

    multiple time

    Need a way to repeat a block of code

    Loops allow repetition

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    The For Loop

    Syntax: for (initialization;test;increment)

    {

    statements;

    }

    The for loop will first perform the initialization.Then, as long test is TRUE, it will execute

    statements. After each execution, it willincrement.

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    For loop

    Known number of iterations

    for(count=1;count

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    For loop examples

    for (x=20 ; x = 20; x -=10) from 80 to 20 in steps of -10

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    While loop

    Unknown number of iterations

    degree =0;

    while (degrees

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    The While Loop

    An example while loop looks like this:

    void main(void)

    {

    char ch;

    while (ch != Q || ch != q)

    {

    ch = getchar( );

    }

    }

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    The Do-while Loop

    The do-while loop repeatedly executes ablock of code indicated by statements aslong as the conditional expressioncond_expr is true.

    do {

    statements;

    } while (cond_expr);

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    A while for for

    i=0;while(i

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    A for for while

    for(; degree

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    Special Cases

    You can have as many controlvariables as you want in loops. Thefollowing is fine:

    for (x=0, y=0; x+y

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    A forever loop

    Using forfor(;;)

    {

    printf(Would you please stop teaching C\n);

    }

    Using while

    while(1)

    {printf(Would you please stop teaching C\n);

    }

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    Fahrenheit-to-Celsius conversionvoid main(void)

    {int deg_c, deg_f;

    deg_c = 0;

    while (deg_c

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    int main()

    {

    int count = 1;

    while (count

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    Continue & Break

    The continue statement is used to forceprogram execution to the bottom of the loop,skipping any statements that come after it.

    The breakstatement is used to haltexecution of a loop prior to the loops normaltest condition being met.

    The exit statement causes the wholeprogram to terminate if it is called within themain program block.

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    Coding for readability

    int main()

    {

    int i,x,y;float z;

    .

    .

    if (x < 7)

    {

    y= 3;

    z= 4.2;}

    else if (x > 23)

    {

    y= 5;

    z= 7.2

    }

    for (i= 1; i < 200; i++) {

    for (j= 1; j < 200; j++ {

    /* Inside both loops */

    }

    /* Inside only the first loop */

    }

    return 0;}

    Right bracket

    level with

    statement whichstarted it

    Always indent after

    a left bracket

    Start a

    left bracket aftera statement