An assembler is a type of software that converts assembly language code into machine code. Assembly language is a low-level programming language that is closely related to the machine code instructions of a specific computer architecture. Machine code, on the other hand, is a set of instructions that can be executed directly by the computer's hardware.

The role of an assembler in computer programming is to perform the conversion from assembly language to machine code. This process involves several steps:

1. Lexical Analysis: The assembler scans the assembly language code and breaks it down into individual tokens, such as instructions, operands, and symbols. It also checks for any syntax errors in the code.

2. Symbol Table Creation: The assembler creates a symbol table that keeps track of all the symbols used in the assembly code. Symbols can include labels, variables, constants, and subroutine names. The symbol table is used to resolve references to these symbols during the assembly process.

3. Address Assignment: The assembler assigns memory addresses to the instructions and data in the assembly code. It may also calculate the relative or absolute addresses for branch instructions and resolve any forward or backward references.

4. Instruction Translation: The assembler translates each assembly language instruction into its equivalent machine code representation. This involves converting the opcode (operation code) and operands into the binary format understood by the computer's hardware.

5. Object Code Generation: The assembler generates the object code, which is the machine code representation of the assembly language program. The object code can be directly executed by the computer's hardware.

By performing these steps, the assembler enables the computer to execute the program written in assembly language. It bridges the gap between the human-readable assembly code and the machine-executable machine code.

In summary, the role of an assembler in computer programming is to convert assembly language code into machine code by performing lexical analysis, symbol table creation, address assignment, instruction translation, and object code generation. This conversion process allows the computer to understand and execute the program at the hardware level.