Symbol table

In computer science, a symbol table is a data structure where each identifier or symbol (referring to variables, constants, procedures, functions, etc.) in a program's code is associated with the necessary information for its functioning. This may come in two main forms:

1. With object file and executables, the "code" is machine code, and the "information" is typically the memory address of the entity referred to by the symbol.
2. With language translators such as a compiler or interpreters, the "code" is generally a source code, and the "information" refers to the entry's declaration or appearance in the source. (Interpreters also need a way to find the entry's "value" in the table, often an address pointing to another data structure.)
3. With intermediate code files, the "information" may be intermediate between the two above types.

A symbol table of the second type usually only exists in memory during the translation process. A symbol table of the first type is embedded in the output of the translation, such as in an ABIobject file for later use. For example, it might be used when loading a dynamic library, during an interactive debugging session, or as a resource for formatting a diagnostic report during or after execution of a program.