View Compilation Error

0_0_9381773_14021.c:2: error: syntax error before '&' token
0_0_9381773_14021.c: In function `swap':
0_0_9381773_14021.c:4: error: `a' undeclared (first use in this function)
0_0_9381773_14021.c:4: error: (Each undeclared identifier is reported only once
0_0_9381773_14021.c:4: error: for each function it appears in.)
0_0_9381773_14021.c:5: error: `b' undeclared (first use in this function)