View Compilation Error

251388_0_10777.c:3: error: syntax error before '&' token
251388_0_10777.c: In function `swap':
251388_0_10777.c:5: error: `a' undeclared (first use in this function)
251388_0_10777.c:5: error: (Each undeclared identifier is reported only once
251388_0_10777.c:5: error: for each function it appears in.)
251388_0_10777.c:6: error: `b' undeclared (first use in this function)