Programming Fundamentals lecture 8
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This document discusses loops in C programming. It describes for, while, and do-while loops. The for loop allows code to be executed a specific number of times, specified with an initialization, condition, and increment statement. The while loop repeats code as long as a condition is true. The do-while loop is similar to the while loop, but the code is executed once before checking the condition. The document also discusses counter-controlled and sentinel-controlled loops, and provides examples of each loop type.
![Constant
In the C programming languages, const is a type qualifier:[a]
a keyword applied to a data type that
indicates that the data is constant (does not vary). You can use const prefix to declare constants
with a specific type as follows −
const type variable = value;
Example
#include <stdio.h>
int main() {
const int LENGTH = 10;
const int WIDTH = 5;
const char NEWLINE = 'n';
int area;
area = LENGTH * WIDTH;
printf("value of area : %d", area);
printf("%c", NEWLINE);
return 0;
}
Output
value of area : 50
#include<stdio.h>
#include<conio.h>
void main()
{
const int std_reg_no;
std_reg_no= 5;
printf(“Value of you have storedis=%d”, std_reg_no);
std_reg_no= 7; .
}](https://image.slidesharecdn.com/08-160728100931/85/Programming-Fundamentals-lecture-8-8-320.jpg)
Programming Fundamentals lecture 8
- 1. 08 RepetitionControl Structure C - Loops You may encounter situations, when a block of code needs to be executed several number of times. In general, statements are executed sequentially: The first statement in a function is executed first, followed by the second, and so on. Programming languages provide various control structures that allow for more complicated execution paths. A loop statement allows us to execute a statement or group of statements multiple times. Or Loops are used to repeat a block of code. Given below is the general form of a loop statement in most of the programming languages − Types ofloops 1. for 2. while 3. do while 1. for loop A for loop is a repetition control structure that allows you to efficiently write a loop that needs to execute a specific number of times. Syntax for ( init; condition;increment) { statement(s); }
- 2. Here is the flow of control in a 'for' loop − The init step is executed first, and only once. This step allows you to declare and initialize any loop control variables. You are not required to put a statement here, as long as a semicolon appears. Next, the condition is evaluated. If it is true, the body of the loop is executed. If it is false, the body of the loop does not execute and the flow of control jumps to the next statement just after the 'for' loop. After the body of the 'for' loop executes, the flow of control jumps back up to the increment statement. This statement allows you to update any loop control variables. This statement can be left blank, as long as a semicolon appears after the condition. The condition is now evaluated again. If it is true, the loop executes and the process repeats itself (body of loop, then increment step, and then again condition). After the condition becomes false, the 'for' loop terminates. Flow Chart
- 3. Example #include <stdio.h> int main () { int a; /* for loop execution */ for( a = 10; a < 20; a = a + 1 ) { printf("value of a: %dn", a); } return 0; } Output value of a: 10 value of a: 11 value of a: 12 value of a: 13 value of a: 14 value of a: 15 value of a: 16 value of a: 17 value of a: 18 value of a: 19 while loop in C A while loop in C programming repeatedly executes a target statement as long as a given condition is true. Syntax while(condition) { statement(s); } Here, statement(s) may be a single statement or a block of statements. The condition may be any expression, and true is any nonzero value. The loop iterates while the condition is true. When the condition becomes false, the program control passes to the line immediately following the loop.
- 4. Flow Diagram Here, the key point to note is that a while loop might not execute at all. When the condition is tested and the result is false, the loop body will be skipped and the first statement after the while loop will be executed. Example #include <stdio.h> int main () { /* local variable definition */ int a = 10; /* while loop execution */ while( a < 20 ) { printf("value of a: %dn", a); a++; } return 0; } Output value of a: 10 value of a: 11 value of a: 12 value of a: 13 value of a: 14 value of a: 15 value of a: 16 value of a: 17 value of a: 18
- 5. value of a: 19 More about loops Based on the nature of the control variables and the kind of value assigned to, the loops may be classified into following two general categories; a) Counter controlled loop b) Sentinel Value controlled loop a) Counter controlled loops: The type of loops, where the number of the execution is known in advance are termed by the counter controlled loop. That means, in this case, the value of the variable which controls the execution of the loop is previously known. The control variable is known as counter. A counter controlled loop is also called definite repetition loop. Example : A while loop is an example of counter controlled loop. sum = 0; n = 1; while (n <= 10) { sum = sum + n*n; n = n+ 1; } Here, the loop will be executed exactly 10 times for n = 1,2,3,......,10. b) Sentinel Value controlled loop : The type of loop where the number of execution of the loop is unknown, is termed by sentinel controlled loop. In this case, the value of the control variable differs within a limitation and the execution can be terminated at any moment as the value of the variable is not controlled by the loop. The control variable in this case is termed by sentinel variable. Example : The following do....while loop is an example of sentinel controlled loop. do { printf(“Input a number.n”); scanf("%d", &num); } while(num>0);
- 6. In the above example, the loop will be executed till the entered value of the variable num is not 0 or less then 0. This is a sentinel controlled loop and here the variable num is a sentinel variable. goto statement in C A goto statement in C programming provides an unconditional jump from the 'goto' to a labeled statement in the same function. Syntax goto label; .. . label: statement; Example #include <stdio.h> int main () { /* local variable definition */ int a = 10; /* do loop execution */ LOOP:do { if( a == 15) { /* skip the iteration */ a = a + 1; goto LOOP; } printf("value of a: %dn", a); a++; } while( a < 20 ); return 0; } Output value of a: 10 value of a: 11 value of a: 12
- 7. value of a: 13 value of a: 14 value of a: 16 value of a: 17 value of a: 18 value of a: 19
- 8. Constant In the C programming languages, const is a type qualifier:[a] a keyword applied to a data type that indicates that the data is constant (does not vary). You can use const prefix to declare constants with a specific type as follows − const type variable = value; Example #include <stdio.h> int main() { const int LENGTH = 10; const int WIDTH = 5; const char NEWLINE = 'n'; int area; area = LENGTH * WIDTH; printf("value of area : %d", area); printf("%c", NEWLINE); return 0; } Output value of area : 50 #include<stdio.h> #include<conio.h> void main() { const int std_reg_no; std_reg_no= 5; printf(“Value of you have storedis=%d”, std_reg_no); std_reg_no= 7; . }
- 9. Error:Cannot modify a const object