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    For Loop ES081 PART B

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    David Alingasa
    For loops are used when the number of iterations is known. The basic syntax of a for loop includes an initialization expression, loop condition, and update expression separated by semicolons. Nested loops allow loops within other loops. While and do-while loops are used when the number of iterations is unknown, with do-while guaranteeing the block runs at least once.

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    For Loop ES081 PART B

    Uploaded by

    David Alingasa
    19 views21 pages
    For loops are used when the number of iterations is known. The basic syntax of a for loop includes an initialization expression, loop condition, and update expression separated by semicolons. Nested loops allow loops within other loops. While and do-while loops are used when the number of iterations is unknown, with do-while guaranteeing the block runs at least once.

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    Computer programming

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    For loops are used when the number of iterations is known. The basic syntax of a for loop includes an initialization expression, loop condition, and update expression separated by semicolons. Nested loops allow loops within other loops. While and do-while loops are used when the number of iterations is unknown, with do-while guaranteeing the block runs at least once.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    19 views21 pages

    For Loop ES081 PART B

    Uploaded by

    David Alingasa
    For loops are used when the number of iterations is known. The basic syntax of a for loop includes an initialization expression, loop condition, and update expression separated by semicolons. Nested loops allow loops within other loops. While and do-while loops are used when the number of iterations is unknown, with do-while guaranteeing the block runs at least once.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    of 21

    Control Flow

    for statement
    - a kind of loop command wherein the execution of the
    statement does not depend on another instruction.
    Syntax:
    for (initialization expression; loop repetition condition; update expression)
    {
    statement/s;
    }
    Basic For Loop Syntax
    For loops are usually used when we know exactly how many
    times we need to execute repeating block of code. It is also
    good for creating definite loops.
    int counter;
    1. Priming: Set 2. Test Condition: 3. Update: Update the
    the start value. Set the stop value. value.

    for (counter =1;counter <= 10;counter++)


    System.out.println (counter); Note that each section is
    separated by a semicolon.
    Control Flow

    Example

    for (c=1; c<=5; c++){


    printf(“Hello World\n”);
    }
    Flowchart of for loop
    For Loop Flowchart
    1. Priming
    Set counter=1

    2. Test TRUE 3a. print counter


    counter
    3b. Update counter++;
    <= 10

    FALSE
    Sample Problems: Implement using for loop
    #include<stdio.h>
    #include<conio.h>
    //Make a C program to input 10 integers and will output their sum
    Problem 1
    int main()
    {
    Make a C program int num, ctr, sum=0; //declaration part
    that will input 10 for(ctr=1; ctr<=10; ctr++)
    {
    numbers. Output the printf("Enter number%d:", ctr);
    sum. scanf("%d", &num);
    sum=sum+num; //can be written also as sum+-=sum;
    }
    printf("The sum is %d", sum);
    return 0;
    }
    Sample Problems: Implement using for loop
    int main()
    {
    int num, ctr, ctr_pos_odd=0, sum_pos_odd=0; //declaration part
    Problem 2 float ave_pos_odd=0.0;
    for(ctr=1; ctr<=10; ctr++)
    { printf("Enter number%d:", ctr);
    Make a C program scanf("%d", &num);
    if(num>0 && num%2!=0)
    to output the { sum_pos_odd+=num;
    ctr_pos_odd++;
    average of all }
    positive odd }
    ave_pos_odd=(float) sum_pos_odd/ctr_pos_odd;
    integers. );
    printf("The average of all positive add ineteger is %0.2f", ave_pos_odd

    return 0;
    }
    Types of Loop

    Additional information on the different


    types of Loops
    Loop types (reminder)
    Indefinite Loop:

     You do not know ahead of time how many times your loop will execute.
     For example, you do not know how many books a person might order.
    Definite Loop:

     You know exactly how many times you want the loop to execute.
     not at compile time necessarily
    Infinite Loop
    You can still end up with an infinite loop when using for loops

    for (counter = 0; counter <= 10; counter--)


    For Loop Variations
     The limit can be a variable:
    for ( i = 1; i <= limit; i++)
     This counts from 1 to limit
     Update may be negative:
    for (i = 100; i >= 1; i--)
     This counts from 100 to 1.
     Update may be greater than 1:
    for (i = 100; i >= 5; i -= 5)
     This counts from 100 to 5 in steps of 5
    While Loop
    While loop is usually used when we do not know exactly how many times we need
    to execute repeating block of code

    while (*)
    {
    /* repeating block of code */
    }

    * Is a condition which is true or false. Ex. Value> 5


    Condition is checked at every iteration start. If condition is true, execution will
    continue, if it is false execution will break.
    Do While
    Do-while loop is usually used when we do not know exactly how many times we need to
    execute repeating block of code, but we know that we need to execute it at least once

    do {
    /* repeating block of code */
    } while (*);

    do-while is same as while loop with difference that the condition is checked at every
    iteration end. Consequence is that repeating block of code in do-while loop is
    always executed at least once.
    When to Use Which Loop ?

    If you know (or can calculate) how many iterations you need
    , then use for loop.
    Otherwise, if it is important that the loop complete at least
    once before checking for the stopping condition, or if it is
    not possible or meaningful to check the stopping
    condition before the loop has executed at least once, then
    use a do-while loop.
    Otherwise use a while loop.
    Loop within a loop (Nested loops)
    C programming language allows to use one loop inside another loop.
    Following section shows few examples to illustrate the concept.

    The syntax for a nested for loop statement in C is as follows:


    for ( init; condition; increment )
    {
    for ( init; condition; increment )
    {
    statement(s);
    }
    statement(s);
    }
    Additional Problems
    Make a C program to output the following
    figures shown below:

    a] *
    **
    * * *
    * * * *
    Solution to Figure a:

    #include<stdio.h>
    #include<conio.h>
    //This program will print a box of asterisks
    int main(){
    int row, col, max_col, max_row;
    printf("Enter maximum rows:");
    scanf("%d", &max_row);
    max_col=max_row; //since figure is square
    for(row=1; row<=max_row; row++) //this is for outer loop: row
    {
    for(col=1; col<=row; col++) //this is for inner loop: column
    {
    printf("*");
    }
    printf("\n"); //this will position the cursor to the next row
    }
    return 0;
    }
    Loop within a loop (Nested loops)
    The syntax for a nested while loop statement in C
    programming language is as follows:
    while(condition)
    {
    while(condition)
    {
    statement(s);
    }
    statement(s);
    }
    Loop within a loop (Nested loops)
    The syntax for a nested do...while loop statement in C programming
    language is as follows:
    do
    {
    statement(s);
    do
    {
    statement(s);
    }while( condition );
    }while( condition );
    Loop within a loop (Nested loops)

    A final note on loop nesting is that you can


    put any type of loop inside of any other type
    of loop. For example, a for loop can be
    inside a while loop or vice versa.
    Loop within a loop (Nested loops)
    Some programmers like to use successive integers i, j, k, l, etc. for use in
    nested for loops. This can be appropriate if the mathematics being
    implemented uses multiple i j k subscripts.
    Other times it can be less confusing to use alternative variables that are more
    meaningful to the problem at hand, such as the r and c variables used above to keep
    track of rows and columns.
    The limits as to how deeply loops may be nested is implementation
    dependent, but is usually too high to be of any concern, except in cases of
    extremely complex or extremely poorly written programs.

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