View Compilation Error

0_0_3980298_24981.c:2: error: syntax error before '&' token
0_0_3980298_24981.c: In function `swap':
0_0_3980298_24981.c:5: error: `a' undeclared (first use in this function)
0_0_3980298_24981.c:5: error: (Each undeclared identifier is reported only once
0_0_3980298_24981.c:5: error: for each function it appears in.)
0_0_3980298_24981.c:6: error: `b' undeclared (first use in this function)