The following rules apply:

• Symbol names must be unique within their scope.
• You can use uppercase letters, lowercase letters, numeric characters, or the underscore character in symbol names. Symbol names are case-sensitive, and all characters in the symbol name are significant.
• Do not use numeric characters for the first character of symbol names, except in numeric local labels.
• Symbols must not use the same name as built-in variable names or predefined symbol names.
• If you use the same name as an instruction mnemonic or directive, use double bars to delimit the symbol name. For example:

  ||ASSERT||

  The bars are not part of the symbol.

• You must not use the symbols |$a|, |$t|, or |$d| as program labels. These are mapping symbols that mark the beginning of A32, T32, and A64 code, and data within the object file. You must not use |$x|in A64 code.
• Symbols beginning with the characters $v are mapping symbols that relate to floating-point code. ARM recommends you avoid using symbols beginning with $v in your source code.

If you have to use a wider range of characters in symbols, for example, when working with compilers, use single bars to delimit the symbol name. For example:

|.text|

The bars are not part of the symbol. You cannot use bars, semicolons, or newlines within the bars.