## C Program To Implement Booth’s Algorithm

Learn how to implement Booth’s Algorithm in C Programming Language. This algorithm is also famously known as **Booth’s Multiplication Algorithm** named after Andrew Donald Booth. The below given code makes use of arrays and binary and decimal conversions.

#### What is Booth’s Algorithm?

Booth’s Algorithm is a multiplication algorithm for multiplying two signed binary numbers in two’s complement notation. The booth’s multiplication algorithm is primarily used in computer architectures. Shifting bits is comparatively faster than adding digits and, therefore, this algorithm has a faster speed of calculation.

Booth’s Algorithm can be done using different methods such as **Right-Shift Arithmetic** and **Right-Shift Circulant**. The booth’s multiplication algorithm helps in **fast multiplication** and **signed multiplication**.

The right shift arithmetic method involves addition of two binary numbers and shift the resultant sum to 1 bit right position. This C Program Implementation of Booth’s Algorithm uses Right Shift Arithmetic method. The right shift circulant method involves shifting the bits to the right 1 bit position and take the last bit in the binary string and append it to the start of the same binary string.

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This algorithm can be implemented adding one of the two predetermined x and y to get a product. This addition will be unsigned binary addition. After this, a rightward arithmetic shift on the final product is to be done. After getting the final result, convert the two’s complement of the product of decimal number.

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#### C Program For Booth’s Algorithm For Signed Multiplication

#include<stdio.h> #include<math.h> void binary(); void sum(int num[]); void arithmetic_shift(); int comparison[5] = {1, 0, 0, 0, 0}; int first_number[5] = {0}, second_number[5] = {0}, anumcp[5] = {0}; int compare_num1[5] = {0}, compare_num2[5] = {0}, product[5] = {0}, result[5] = {0}; int num1 = 0, num2 = 0, num3 = 0; int m = 0, n = 0; int main() { int count, x = 0; printf("Enter Two Numbers to Multiply (Less Than 16)\n"); do { printf("Enter A:\t"); scanf("%d", &num1); printf("Enter B:\t"); scanf("%d", &num2); }while(num1 >=16 || num2 >=16); printf("\nExpected Product of %d * %d = %d", num1, num2, num1 * num2); binary(); printf("\n\nBinary Equivalents\n"); printf("\nA:\t"); for(count = 4; count >= 0; count--) { printf("%d", first_number[count]); } printf("\nB:\t"); for(count = 4; count >= 0; count--) { printf("%d", second_number[count]); } printf("\nB'+ 1 = "); for(count = 4; count >= 0; count--) { printf("%d", compare_num2[count]); } printf("\n"); for(count = 0; count < 5; count++) { if(first_number[count] == x) { printf("\n-->"); arithmetic_shift(); x = first_number[count]; } else if(first_number[count] == 1 && x == 0) { printf("\n-->"); printf("\nSUB B: "); sum(compare_num2); arithmetic_shift(); x = first_number[count]; } else { printf("\n-->"); printf("\nADD B: "); sum(second_number); arithmetic_shift(); x = first_number[count]; } } printf("\nProduct:\t"); for(count = 4; count >= 0; count--) { printf("%d", product[count]); } for(count = 4; count >= 0; count--) { printf("%d", anumcp[count]); } printf("\n"); return 0; } void binary() { m = fabs(num1); n = fabs(num2); int r2, remainder, count, temp; for(count = 0; count < 5; count++) { remainder = m % 2; m = m / 2; r2 = n % 2; n = n / 2; first_number[count] = remainder; anumcp[count] = remainder; second_number[count] = r2; if(r2 == 0) { compare_num2[count] = 1; } if(remainder == 0) { compare_num1[count] =1; } } num3 = 0; for(count = 0; count < 5; count++) { result[count] = comparison[count]+ compare_num2[count] + num3; if(result[count] >= 2) { num3 = 1; } else { num3 = 0; } result[count] = result[count] % 2; } for(count = 4; count >= 0; count--) { compare_num2[count] = result[count]; } if(num1 < 0) { num3 = 0; for(count = 4; count >= 0; count--) { result[count] = 0; } for(count = 0; count < 5; count++) { result[count] = comparison[count] + compare_num1[count] + num3; if(result[count] >= 2) { num3 = 1; } else { num3 = 0; } result[count] = result[count] % 2; } for(count = 4; count >= 0; count--) { first_number[count] = result[count]; anumcp[count] = result[count]; } } if(num2 < 0) { for(count = 0; count < 5; count++) { temp = second_number[count]; second_number[count] = compare_num2[count]; compare_num2[count] = temp; } } } void sum(int num[]) { int count; num3 = 0; for(count = 0; count < 5; count++) { result[count] = product[count] + num[count] + num3; if(result[count] >= 2) { num3 = 1; } else { num3 = 0; } result[count] = result[count] % 2; } for(count = 4; count >= 0; count--) { product[count] = result[count]; printf("%d", product[count]); } printf(":"); for(count = 4; count >= 0; count--) { printf("%d", anumcp[count]); } } void arithmetic_shift() { int x = product[4], y = product[0], count; for(count = 1; count < 5 ; count++) { product[count - 1] = product[count]; } product[4] = x; for(count = 1; count < 5; count++) { anumcp[count - 1] = anumcp[count]; } anumcp[4] = y; printf("\nArithmetic Shift"); for(count = 4; count >= 0; count--) { printf("%d", product[count]); } printf(":"); for(count = 4; count >= 0; count--) { printf("%d", anumcp[count]); } }

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#### Output

If you have any compilation errors or doubts in this C Program for Booth’s Multiplication Algorithm Implementation, let us know about it in the comment section below.

The Booth’s algorithm is really difficult to understand. Normal additiin is good. 😛

I had not heard of Booth’ algorithm before. This is something new for me.

Shifting of bits or bit manipulation is faster than actual addition of integers. Therefore, this algorithm works so fast.