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    Cis 1101 - Programming 1: Function in C

    Uploaded by

    Marvin Go
    This document discusses C functions, including defining functions, calling functions, and passing parameters by value versus by reference. It provides examples of function definitions and calls, discusses how the call stack works when calling a function, and shows examples of passing parameters by value and by reference, including sample code to swap the values of two variables using each approach.

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    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd

    Cis 1101 - Programming 1: Function in C

    Uploaded by

    Marvin Go
    43 views8 pages
    This document discusses C functions, including defining functions, calling functions, and passing parameters by value versus by reference. It provides examples of function definitions and calls, discusses how the call stack works when calling a function, and shows examples of passing parameters by value and by reference, including sample code to swap the values of two variables using each approach.

    Original Title

    Fucntion P2

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    © © All Rights Reserved

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    This document discusses C functions, including defining functions, calling functions, and passing parameters by value versus by reference. It provides examples of function definitions and calls, discusses how the call stack works when calling a function, and shows examples of passing parameters by value and by reference, including sample code to swap the values of two variables using each approach.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    43 views8 pages

    Cis 1101 - Programming 1: Function in C

    Uploaded by

    Marvin Go
    This document discusses C functions, including defining functions, calling functions, and passing parameters by value versus by reference. It provides examples of function definitions and calls, discusses how the call stack works when calling a function, and shows examples of passing parameters by value and by reference, including sample code to swap the values of two variables using each approach.

    Copyright:

    © All Rights Reserved
    Download as PDF, TXT or read online from Scribd
    Download as pdf or txt
    You are on page 1of 8

    24 Mar 2020

    CIS 1101 – PROGRAMMING 1

    FUNCTION IN C

    Part 2

    C FUNCTION: C FUNCTION ASPECTS

    C Function Aspects Syntax

    Function definition: Return_type function_name (parameters list)


     Function Header {
     Function Body Body of the function;
    }

    Function call Function_name (arguments list);

    Function declaration Return_type function_name (parameters list);


    (or prototype)

    2
    24 Mar 2020

    C FUNCTION: STEPS IN FUNCTION CREATION

    1. Write the Function Header.


     int calcSum(int x, int y)

    2. Write a sample Function Call.


     Declare and initialize (if needed) the variables
    used in the call and place them before the call.

    C FUNCTION: FUNCTION CALL

    Sample Function Call

    int a, b;
    int total;
    a = 75;
    b = 86;

    total = calcSum(a,b);

    4
    24 Mar 2020

    C FUNCTION: STEPS IN FUNCTION CREATION

    3. Assume that the function call is in main().


     Draw the execution stack.
     Label the variables with names, values, and addresses.

    C FUNCTION: EXECUTION STACK

    Local variable Parameters

    sum x y  Activation Record of calcSum()


    • Pass-By-Copy (Call-By-Value )
    ? ? ?

    B700 B500 B600

    a b total  Activation Record of main()


    • total = calcSum (a, b);
    ? ? ?

    A100 A200 A300

    6
    24 Mar 2020

    C FUNCTION: STEPS IN FUNCTION CREATION

    4. Write the code of the function.


     If the return type is not void,
    • declare the local variable of the return type first
    • then write the return statement.

    CALLING A C FUNCTION: CALL-BY-VALUE/PASS-BY-VALUE

     The value of the variable


    is passed to the function
    as parameter.

     The value of the actual parameter


    variable is passed (or copied) into
    the formal parameter variable.

     It is also known as Pass-By-Copy.

    8
    24 Mar 2020

    CALLING A C FUNCTION: CALL-BY-VALUE/PASS-BY-VALUE

     The value of the actual parameter


    cannot be modified by formal
    parameter.

     Different memory is allocated for both


    actual and formal parameters because
    value of the actual parameter is copied to
    formal parameter.

    ACTUAL PARAMETER(S) VERSUS FORMAL PARAMETER(S)

     Actual parameter:
    • The actual value that is passed into the function
    by a caller, and it is often called as argument.

     Formal parameter:
    • The identifier used in a function to stand for the
    value that is passed into the function by a caller.

    10
    24 Mar 2020

    CALLING A C FUNCTION: CALL-BY-REFERENCE

     The address of the variable is passed


    to the function as parameter.

     The value of the actual parameter can be modified by


    formal parameter.

     Same memory is used for both actual and formal


    parameters since only address is used by both parameters.

    11

    CALLING A C FUNCTION: CALL-BY-REFERENCE

     The location (reference or address) of the actual


    parameter variable is passed (or copied) into
    the formal parameter variable.

     It is also known as Pass-By-Reference.

    12
    24 Mar 2020

    CALLING A FUNCTION: SAMPLE


    Given:
    A program uses two variables d and e and it assigns d with a value of 30 and
    e with 50. Then it will swap those values.
    Tasks:
    a) Create a function that will swap the values assigned to the given two variables d and e using
    Pass-By-Value.

    b) Write the code of the program described above using the created function and verify its output.

    c) Create a function using pointers that will swap the values assigned to the given two variables d
    and e using Pass-By-Reference.

    d) Write the code of the program described above using the created function and verify its output.

    13

    CALLING A FUNCTION: SAMPLE


    #include<stdio.h>
    /* function prototype, also called function declaration */
    void swap(int, int);
    int main() C FUNCTION PROGRAM
    { (USING PASS-BY-VALUE):
    int d = 30, e = 50;
    /* Calling swap function by value */ In this program, the values
    printf(“\nThe values before swapping: \nd = %d \ne = %d\n", d, e);
    of the variables “d” and
    swap(d,e);
    printf("\nThe values after swapping: \nd= %d \ne = %d\n", d, e); “e” are passed to the
    return 0; function “swap”.
    }
    /* Swap function definition */ These values are copied to
    void swap(int a, int b) formal parameters “a”
    { and “b” in swap function
    int tmp; and used.
    tmp = a;
    a = b;
    b = tmp;
    }

    14
    24 Mar 2020

    CALLING A FUNCTION: SAMPLE


    #include<stdio.h>
    /* Function prototype, also called function declaration */
    void swap(int*, int*); C FUNCTION PROGRAM
    (USING PASS- BY-REFERENCE):
    int main()
    { In this program, the address of the
    int d = 30, e = 50; variables “d” and “e” are passed
    /* Calling swap function by reference */ to the function “swap”.
    printf(“The values before swapping: \nd = %d \ne = %d\n", d, e);
    swap(&d, &e); These values are not copied to
    printf(“\nThe values after swapping: \nd = %d \ne = %d\n", d, e); formal parameters “a” and “b”
    return 0; in swap function because they
    } are just holding the address of
    those variables.
    void swap(int *a, int *b)
    { This address is used to access
    int tmp; and change the values of the
    tmp = *a; variables.
    *a = *b;
    *b = tmp;
    }

    15

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