C# Multiply Numbers: Multiplication TableMultiply ints with the multiply operator. Consider aspects of multiplication.
Multiply. The multiply operator is an asterisk. It computes the product of 2 numbers. This is the same in the C# language as in many other programming languages.
This operator obeys the operator precedence rules. So we can mix additions and multiplications and multiplication will come first.
We compute the product of 2 operands using the multiplication operator. You can multiply any 2 numbers that can be implicitly converted to compatible types.
Predefined: The C# language specification defines many predefined arguments (int, double) for the multiplication operator.Int, uintDouble
Here: We compute the product of 100 and 5. The number 100 is a constant. The value 5 was determined at program runtime.
Note: Because one value was not known at compile-time, the C# compiler cannot compute the product of the operands statically.
C# program that multiplies numbers
static void Main()
// Use a constant local and a dynamically
// ... determined integer as operands.
const int operand1 = 100;
int operand2 = int.Parse("5");
// Compute the product and store it in a local variable.
int product = operand1 * operand2;
// You can check the value of a multiple expression in an if-statement.
if ((operand1 * operand2) == 500)
// You can multiply a number against itself.
operand2 *= 2;
Console.WriteLine(operand2); // Now equal to 10 not 5.
The multiplication operator has a greater precedence than plus or minus. The rules for operator precedence in the C# language are the same as those for arithmetic.
Tip: The C# language has additional rules for coding-specific operators not found in regular mathematics.
Next we write a multiplication table program. It uses two nested for-loops. The numbers we loop over are in the range 1 to 9.
Info: In the innermost statement, we use the multiplication operator and then use a ToString format pattern.For
Also: A new line is printed at the end of each nine numbers in the loop. This improves the output format.
C# program that creates multiplication table
static void Main()
// Loop through all operands in the multiplication table.
for (int a = 1; a < 10; a++)
for (int b = 1; b < 10; b++)
// Write the multiplied number.
Console.Write((a * b).ToString("00 "));
// New line.
01 02 03 04 05 06 07 08 09
02 04 06 08 10 12 14 16 18
03 06 09 12 15 18 21 24 27
04 08 12 16 20 24 28 32 36
05 10 15 20 25 30 35 40 45
06 12 18 24 30 36 42 48 54
07 14 21 28 35 42 49 56 63
08 16 24 32 40 48 56 64 72
09 18 27 36 45 54 63 72 81
Concepts. In programs, multiplications are more expensive than additions. Many strategies are meant to reduce them, such as strength reduction for affine expressions.
This refers to replacing an expensive (strong) expression, such as one that uses multiplication or division, with cheap operations such as addition.
Note: At first strength reduction might not seem like a common optimization. We might not specify multiplication that often.
However: It is actually used for array accesses. These must address an element based on a multiple of the element size.
Affine expressions, data reuse.
Compilers implement optimizations based on the concept of affine expressions, which are expressions in loops that are multiplied or added by a constant.
Therefore: Many array accesses and loop indexes may involve multiplications. And these are not explicit in the source code.
Finally: Compilers also try to understand data reuse to improve locality of reference in subsequent loops.
A summary. We looked at multiplying numbers. The multiplication operator is the star character. The compound operator is represented by the *= characters.
© 2007-2020 Sam Allen. Every person is special and unique. Send bug reports to firstname.lastname@example.org.