# and ## Operators in C

In this article, we will discuss the # and ## operators in C with their syntax and examples.

What is the # operator?

The stringizing operator (#) is a preprocessing operator that causes the corresponding real argument to be surrounded by a pair of quotation marks. The stringize operator is often known as the # operator. It converts the input it precedes into a quotation string. It's commonly referred to as the stringification operator. It is usually utilized with macros in C.

Syntax:

It has the following syntax:

Example:

Output:

 Programming 

Explanation:

• The mkstr macro is invoked with the parameter Programming.
• The macro's # operator turns Programming into the character literal "Programming".
• After that, the printf function writes the string "Programming" to the terminal.

As a result, when an application runs, it prints the string "Programming" on the terminal. The # operator in the macros definition turns the argument's value into a string literal, enabling the text to be displayed as a string.

What is the token-pasting operator (##)?

Tokens used as real arguments can be concatenated using the Token-pasting operator (##). When extending macros, it is frequently advantageous to combine two tokens into one. It is referred to as token pasting or token conjunction.

The token pasting is done by the '##' pre-processing operator. When a macro is extended, the two tokens on both sides of each '##' operator are merged into a single token, which replaces the '##' and the two original tokens within the macro expansions.

Syntax:

It has the following syntax:

Example:

Output:

 39 

Explanation:

• A macro concat(a, b) that concatenates a and b without any spaces in between using the ## operator. After that, defined a variable of type integer mn with the value 39 in the main function.
• The printf command concatenates m and n using the concat macro, producing the resultant token mn. It essentially replaces concat(m, n) with mn.
• When the code is performed and printf is called, the current value of the variable mn will be shown, which is 39, because mn was defined as an integer containing an integer value of 39.

Advantages of # and ## Operators:

There are several advantages of the # and ## operators. Some main advantages of these operators are as follows:

# Operator

• Debugging and Logging: It is extremely useful for debugging and logging. For example, it can be used to transform macro parameters into strings that can be indicated for debugging purposes.
• General Macros: It allows for the design of more general macros that interact with various kinds of values, transforming them to string representation for specified operations.

## Operator

• Creating New Identifiers: It enables the creation of new identifiers or symbols by merging previously used ones. It is very useful for dynamically creating variable or function names.
• Code Reusability: It helps in the creation of more generic and reusable code using macros. For example, similar functions or structures must be produced under different names in data structure implementations.