Global variables, sorting static variables,function and arrays,

GROUP # 04

GROUP MEMBERS;

HAFIZ AHMAD ALI EN-15024

SAQIB KHOKHAR EN-15017

HASNAIN BILAL EN-15025

GLOBAL VARIABLE

• GLOBAL VARIABLES HOLD THEIR VALUES THROUGHOUT THE LIFETIME OF YOUR PROGRAM AND THEY CAN BE ACCESSED INSIDE ANY OF THE FUNCTIONS DEFINED FOR THE PROGRAM.

• GLOBAL AND LOCAL VARIABLES

• A LOCAL VARIABLE IS A VARIABLE THAT IS DECLARED INSIDE A FUNCTION.

• A GLOBAL VARIABLE IS A VARIABLE THAT IS DECLARED OUTSIDE ALL FUNCTIONS.

• A LOCAL VARIABLE CAN ONLY BE USED IN THE FUNCTION WHERE IT IS DECLARED.

• A GLOBAL VARIABLE CAN BE USED IN ALL FUNCTIONS.

#include<stdio.h> // Global variables int A; int B; int Add() { return A + B; } int main() { int answer; // Local variable A = 5; B = 7; answer = Add(); printf("%d\n",answer); return 0; }

Sorting

To arrange a set of items in sequence.

Many applications require sorting;

Many applications perform sorting when they don't have to;

Many applications use inefficient sorting algorithms.

Sorting Applications

To prepare a list of student ID, names, and scores in a table (sorted by ID or name) for easy checking.

To prepare a list of scores before letter grade assignment.

To produce a list of horses after a race (sorted by the finishing times) for payoff calculation.

To prepare an originally unsorted array for ordered binary searching.

Static and Automatic Variables

• Automatic variable - memory is allocated at block entry and deallocated at block exit

• Static variable - memory remains allocated as long as the program executes

• Variables declared outside of any block are static variables

• By default, variables declared within a block are automatic variables

• Declare a static variable within a block by using the reserved word static

Static and Automatic Variables (continued)

• The syntax for declaring a static variable is:

static dataType identifier;

• The statement

static int x;

declares x to be a static variable of the type int

• Static variables declared within a block are local to the block

• Their scope is the same as any other local identifier of that block

Summary (continued)

• An automatic variable is a variable for which memory is allocated on function (or block) entry and deallocated on function (or block) exit

• A static variable is a variable for which memory remains allocated throughout the execution of the program

• C allows functions to have default parameters

C FUNCTIONS

Basically there are two categories of function:

1. Predefined functions: available in C / C++

standard library such as stdio.h, math.h,

string.h etc.

2. User-defined functions: functions that

programmers create for specialized tasks such

as graphic and multimedia libraries,

implementation extensions or dependent etc.

FUNCTION & ARRAY:

FOR A FUNCTION TO RECEIVE AN ARRAY THROUGH A FUNCTION CALL, THE

FUNCTION’S PARAMETER LIST MUST SPECIFY THAT AN ARRAY WILL BE RECEIVED.

SYNTAX

INDICATING THAT MODIFY ARRAY EXPECTS TO RECEIVE AN ARRAY OF INTEGERS

IN PARAMETER B AND THE NUMBER OF ARRAY ELEMENTS IN PARAMETER SIZE.

THE SIZE OF THE ARRAY IS NOT REQUIRED BETWEEN

THE ARRAY BRACKETS.

#include <stdio.h>

float average(float a[]);

int main(){

float avg, c[]={23.4, 55, 22.6, 3, 40.5, 18};

avg=average(c); /* Only name of array is passed as argument. */

printf("Average age=%.2f",avg);

return 0;

}

float average(float a[ ])

{

int i;

float avg, sum=0.0;

for(i=0;i<6;++i){

sum+=a[i];

}

avg =(sum/6);

return avg;

}

Output Average age=27.08

C program to pass an array containing age of person to a function. This function should find averageage and display the average age in main function.

#include

void Function(int c[2][2]);

int main(){

int c[2][2],i,j;

printf("Enter 4 numbers:\n");

for(i=0;i<2;++i)

for(j=0;j<2;++j){

scanf("%d",&c[i][j]);

}

Function(c); /* passing multi-dimensional array to function */

return 0;

}

void Function(int c[2][2]){

/* Instead to above line, void Function(int c[][2]){ is also valid */

int i,j;

printf("Displaying:\n");

for(i=0;i<2;++i)

for(j=0;j<2;++j)

printf("%d\n",c[i][j]);

} Output

Enter 4 numbers:

2

3

4

5

Displaying:

2

3

4

5