1. ‘C’ Programming
Khalid Jamal

2. SCANF()

4. SCANF FOR FLOAT (REAL VALUES)

5. Example

6. Scanf – specification for strings
%[characters]  means that only the characters specified in the brackets are permissible in the input string %[^characters]  does exactly the reverse, the characters specified after (^) are not permitted
main() {
int no;
char address[80];
printf("Enter No. and Address: ");
scanf("%d %[a-z]",&no, address);
printf("%d %s", no, address); }
Enter No. and Address: new delhi
new delhi

7. Decision Making and Branching
We know that C program is a set of statements which are normally executed in a sequential manner. Suppose, we need to change the order of execution of statements based on certain conditions or repeat a group of statements until certain condition is satisfied. This involves a kind of decision making to see whether a particular condition has occurred or not.

8. Decision Making Statements
C language possesses decision making capabilities by supporting 
if statement
switch statement
Conditional operator statement
goto statement
These statements are popularly known as decision-making statements. Since these statements control the flow of execution, hence they are also called control statements

9. IF STATEMENT
It is powerful two-way decision making statement, used along with an expression

10. IF Example
PROBLEM 
Write a C Program to find that the given number is even or odd

11. Executed only when IF condition is true
IF-ELSE Statement
Executed only when IF condition is true

12. If-Else Sample ......... if(code == 1) x = x + 1; if(code == 2)
Only IF Condition
Using If-Else Condition
if(code == 1)
x = x + 1;
if(code == 2)
y = y +1;
if(code == 1)
x = x + 1;
else
y = y +1;

13. Example
Write a C program to find the small of two numbers using if-else statement

14. Applying De-Morgan Law
While implementing decision statements, we often face situations where the logical NOT operator is applied to a compound logical expression like !(x&&y || !z). However, a positive logic is easy to apply. In those cases, we apply DE- MORGAN’s LAW Remove parenthesis by applying NOT operator to every logical expression, while complementing relational operator

15. Example
!(x&&y || !z) That is  x becomes !x !x becomes x && becomes || || becomes && Ex !(x && y || !z) becomes !x || !y && z !(x <=0 || !condition) becomes x>0 && condition

16. Nesting of If-Else Statement
When a series of decisions are involved, we may have to use more than one if…else statement in nested form.
If condition-1 is false, statement-3 will be executed otherwise it continues to perform second test. If condition -2 is true, statement-1will be evaluated; otherwise statement-2will be evaluated and then control is transferred to statement-x

17. Example of Nested If-Else (Flow-chart)

18. Find Largest of 3 numbers using nested if-else

19. Sample program
Write a C program to find largest of 3 numbers using nested if-else with the help of given flow chart

20. Dangling Else Problem
One of the classic problem encountered when we start using nested if…else statements is dangling else. This occurs when a matching else is not available for an if. The answer is very simple, always match an else to the most recent unmatched if in the current block. In some cases, false condition may not be required, in that case else can be omitted. NOTE else is always paired with most recent unpaired if

21. Dangling Else Problem (contd.)

22. Dangling Else Problem (contd.)

23. The Else-If Ladder
There is another way of putting if’s together when multiple decisions have to be taken. In that case, chain of if’s in which statement associated with each else is an if.
This construct is known as the else if ladder. The conditions are evaluated from the top, downwards. As soon as true condition is found, statement associated with it is executed and control is transferred to statement-x (skipping rest of the ladder)

24. Else-If Ladder Flowchart
if(marks >= 75)
grade="honors";
else if (marks >= 60)
grade="first division";
else if (marks >=45)
grade="second division";
else if (marks >=30)
grade="third division";
else
grade="fail";
printf ("%s", grade);

25. Sample Program Consumption Units Rate of Charge 0-200
An electric distribution company charges its domestic consumer as follows Write a C program which reads no. of units consumed and give amount to be paid by customer using else-if ladder. 150, 225, 375, 520, 625
Consumption Units
Rate of Charge
0-200
Rs per unit
Rs Rs per unit
Rs Rs per unit
601 and above
Rs Rs per unit

26. Indentation Rules
Align vertically else clause with their matching if clause
Use braces on separate lines to identify block of statements
Indent the statements to the right inside the braces
Align the opening and closing braces
Use appropriate comments to signify the beginning and end of code blocks
Code only one clause or statement in one line

27. Indentation Rules Sample

28. The switch statement
When one of many alternatives to be selected, we can use if statement to control the selection. However, complexity of such a program increases dramatically when number of alternatives increases. The program becomes difficult to read and follow. C has a in-built multi-way decision statement known as switch. The switch tests value of given variable (or expression) against a list of case values, when a match is found, block of statement associated with that case is executed

29. Switch Sample, BREAK & DEAFULT
BREAK statement is used to exit from loop or switch and control is passed to the first statement beyond loop or switch. BREAK statement is optional. Two or more case labels may follow same statements.
DEFAULT label is also optional. If present executed only when no matching case is found. There can be only 1 default.

30. Switch Case Example index=marks/10; switch(index) {
case 10: case 9: case 8: grade=“honours”; break; case 7: case 6: grade=“first div”;
break; case 5: grade=“sec. div”; break;
case 4: grade=“third div”;
break;
default: grade=“fail”; }
printf(“%s”, grade);

31. The ? : Operator
The C language has an unusual operator, useful for making two-way decisions. The combination of ? : popularly known as conditional operator (ternary operator)

32. Examples
y = (x > 2) ? (2 * x +5) : (1.5 * x + 3) The conditional operator may be nested for evaluating more complex assignment decisions 4x for x < 40 Salary = 300 for x = x for x > 40 This complex equation can be written as  salary = (x != 40) ? ((x<40) ? (4*x + 100) : (4.5*x + 150)) : 300;

33. Example (contd.)
The same can be evaluated using if…else statements IF (X <= 40) IF (X < 40) SALARY = 4 * X +100; ELSE SALARY = 300; ELSE SALARY = 4.5 * X +150;

34. The goto statement
The goto statement is used to alter the normal sequence of program execution by transferring control to some other part of the program unconditionally. In its general form, the goto statement is written as goto label; where the label is an identifier that is used to label the target statement to which the control is transferred. Control may be transferred to anywhere within the current function. Each labeled statement within the function must have a unique label, i.e., no two statement can have the same label.

35. GOTO EXAMPLE

36. Decision Making and Looping
Suppose we need to calculate sum of squares of all integers between 1 and 10. We can write program using if & goto statements
Initializes the variable n.
Computes square of n and add to sum
Test the value of n to check whether it is equal to 10 or not. If it is equal to 10, then print the result.
If n<10, increment by one and compute again.
loop
N = 10 end of loop

37. Looping & Its Structure
Loops are used to execute a block of code several times
There are 3 types of loops in C
While
Do-while
For loop

38. While Loop

39. Flow Chart of While Loop

40. Example of While Loop
Output  1 2 3 4 5 6 7 8 9

41. Problem Y=Xn N is positive integer
Write a C program to evaluate the equation using while loop
Y=Xn
N is positive integer

42. Solution

43. Do-while statement
A do-while loop is similar to a while loop, except that a do...while loop is guaranteed to execute at least one time. Notice that the conditional expression appears at the end of the loop, so the statement(s) in the loop execute once before the condition is tested.

44. Flow Chart of Do-While

45. Do-While Example

46. Another Example

47. While versus Do-While

48. While versus Do-While

49. Problem
Write a C Program to find and print first n – Fibonacci numbers using do-while loop  Write a C program to find factorial of number n using while loop

50. For Loop
Like While loop, for loop is entry controlled loop. i.e. conditions are checked if found true then and then only code is executed

51. Working
The initialization statement is executed only once at the beginning of the for loop. Then the test expression is checked by the program. If the test expression is false, for loop is terminated. But if test expression is true then the code/s inside body of for loop is executed and then update expression is updated. This process repeats until test expression is false.

52. Flow Chart

53. Problem
Write a C program to find factorial of number n using while loop Write Programs to print following output using for loops

54. Some More Problems

55. Factorial using while loop

56. Factorial using for loop

57. Fibonacci Series using while loop

58. Fibonacci Series using for loop

59. C Program to print right triangle using for loop
Expected Output
Actual Output

60. C Program to print number pattern
Expected Output
Actual Output

61. C Program to print simple triangle

62. C Program to print Upside Down Triangle

63. C Program to print hollow diamond

64. Problems

65. One MORE PROBLEM