以井号开头的行和gcc预处理器输出中的'＃1“ac”'之类的数字是什么意思？

我使用打印出C预处理器的输出

gcc -E a.c

输出包含许多行

# 1 "a.c"

# 1 ""

# 1 ""

# 1 "a.c"

# 1 "c:\\mingw\\bin\\../lib/gcc/mingw32/4.5.0/../../../../include/stdio.h" 1 3

# 19 "c:\\mingw\\bin\\../lib/gcc/mingw32/4.5.0/../../../../include/stdio.h" 3

# 1 "c:\\mingw\\bin\\../lib/gcc/mingw32/4.5.0/../../../../include/_mingw.h" 1 3

# 31 "c:\\mingw\\bin\\../lib/gcc/mingw32/4.5.0/../../../../include/_mingw.h" 3

# 32 "c:\\mingw\\bin\\../lib/gcc/mingw32/4.5.0/../../../../include/_mingw.h" 3

# 20 "c:\\mingw\\bin\\../lib/gcc/mingw32/4.5.0/../../../../include/stdio.h" 2 3

我从未在C中看到过这种语法。有人可以解释这是做什么的吗？