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5.3 Symbol Names
Symbol names begin with a letter or with one of `._'. On most
machines, you can also use
Case of letters is significant: Each symbol has exactly one name. Each name in an assembly language program refers to exactly one symbol. You may use that symbol name any number of times in a program. Local Symbol NamesLocal symbols help compilers and programmers use names temporarily. There are ten local symbol names, which are re-used throughout the program. You may refer to them using the names `0' `1' ... `9'. To define a local symbol, write a label of the form `N:' (where N represents any digit). To refer to the most recent previous definition of that symbol write `Nb', using the same digit as when you defined the label. To refer to the next definition of a local label, write `Nf'---where N gives you a choice of 10 forward references. The `b' stands for "backwards" and the `f' stands for "forwards". Local symbols are not emitted by the current GNU C compiler. There is no restriction on how you can use these labels, but remember that at any point in the assembly you can refer to at most 10 prior local labels and to at most 10 forward local labels. Local symbol names are only a notation device. They are immediately transformed into more conventional symbol names before the assembler uses them. The symbol names stored in the symbol table, appearing in error messages and optionally emitted to the object file have these parts:
For instance, the first
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