by Dinesh Thakur Category: Control Structures

The program segment given below determines the sum of digits of a given number repeatedly until a single digit number is obtained. For example, 5985 => 27 => 9, where symbol => indicates a digit sum operation. Thus, if digit sum exceeds 9, it is used as a number for subsequent digit sum operations.

 
by Dinesh Thakur Category: Control Structures

The while loop is particularly useful when the number of iterations is not known or cannot be determined in advance. The general syntax of the while loop is as follows:

 
by Dinesh Thakur Category: Control Structures

The program segment given below uses a nested if statement to determine whether a given character is a letter or not. In addition, if the given character is a letter, it tests whether it is a vowel or consonant.

 
by Dinesh Thakur Category: Control Structures

The switch statement allows us to test an expression and depending on its value, execute a statement (or group of statements) amongst several alternatives. It is the most involved statement provided in C language. It uses four keywords, namely, switch, case, default and break. The last two keywords are optional and can be omitted. The general form of this statement is given below and its flowchart is shown in.

 
by Dinesh Thakur Category: Control Structures

The C program computes the rational approximation to a given real number, i.e., given a real number val, the program computes a pair of integers N and D such that the fraction N/D is a good approximation to val. To do so, we use the following series of steps.

 
by Dinesh Thakur Category: Control Structures

These statements determine and print the absolute value of variable n. If n is negative, then n < 0 evaluates as true and n is assigned the value of -n, which is then printed in the next statement assuming variable n to be of some integer type. However, if the value of n is positive, it remains unchanged and is printed.

 
by Dinesh Thakur Category: Control Structures

The Greatest Common Divisor of two positive integers can be calculated iteratively by the following formula known as Euclid's algorithm. You can see that this is a recursive definition with GCD(m,n) defined in terms of GCD(n,m%n).

 
by Dinesh Thakur Category: Control Structures

The if-else statement given below uses the leap year test to determine the number of days in February.

 
by Dinesh Thakur Category: Control Structures

The program segment given below obtains a number by reversing the digits in the given number.

 
by Dinesh Thakur Category: Control Structures

Consider that we wish to determine the result of a student in the SSC (Secondary School Certificate) examination, which has six subjects: four of 100 marks each and two of 150 marks each.

 
by Dinesh Thakur Category: Control Structures

In this example, we use two for loops in conjunction with the putchar library function to print all uppercase letters followed by all lowercase letters. The loop variable ch is assumed to be of type char or int. The first for loop prints the uppercase letters as loop variable ch assumes values as ‘A’, 'B’, ... , ‘z’.

 
by Dinesh Thakur Category: Control Structures

Perfect numbers are positive integers which have the special property that the sum of all their factors equals the number itself, e.g., 6 = 1+2+3. The C program finds and prints out all perfect numbers less than 1000.

 
by Dinesh Thakur Category: Control Structures

The trapezoidal rule is the simplest method to approximate the definite integral of a function f(x) over the interval [a, b]. Given N equally space points (with a spacing of h) X0, X1, ..., XN such that X0 = a and XN = b, the integral of f(x) can be approximated as the sum

 
by Dinesh Thakur Category: Control Structures

Let us use variables a and b of type float to represent two operands, variable c of type float to represent the result and variable op of type char to represent the operator. In the program given below, an expression of the form a op b is first accepted from the keyboard and a switch statement is used to evaluate the result.

 
by Dinesh Thakur Category: Control Structures

The continue statement is another loop interruption statement provided in the C language. It interrupts only the current iteration of the loop as opposed to the break statement which interrupts the execution of the entire loop. The format of the continue statement is as follows:

 
by Dinesh Thakur Category: Control Structures

The while loop is particularly suitable when the number of iterations is not known or can not be determined in advanced. In this section, another loop that is useful in similar situations, the do ... while loop is discussed.

 
by Dinesh Thakur Category: Control Structures

Consider that we have to add the given numbers until the desired sum is obtained (i. e., as long as the sum is less than a specified value).

 
by Dinesh Thakur Category: Control Structures

The for loop is used for repetitive execution of a statement or a group of statements. It is a very powerful and flexible statement of the C language. It is generally used in situations where the number of iterations of the loop statement is known or can be determined in advance.

 
by Dinesh Thakur Category: Control Structures

The program segment given below reads a number from the keyboard (in variable num of type float) and prints its square root. However, as the sqrt function requires a non-negative argument, the program uses a do ..while loop to read the data until valid data is entered.

 

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About Dinesh Thakur

Dinesh ThakurDinesh Thakur holds an B.SC (Computer Science), MCSE, MCDBA, CCNA, CCNP, A+, SCJP certifications. Dinesh authors the hugely popular blog. Where he writes how-to guides around Computer fundamental , computer software, Computer programming, and web apps. For any type of query or something that you think is missing, please feel free to Contact us.