View Compilation Error

0_0_2645064_7412.c:3: error: syntax error before '&' token
0_0_2645064_7412.c: In function `change':
0_0_2645064_7412.c:6: error: `b' undeclared (first use in this function)
0_0_2645064_7412.c:6: error: (Each undeclared identifier is reported only once
0_0_2645064_7412.c:6: error: for each function it appears in.)