View Compilation Error

61613_0_25008.c: In function `is_prime':
61613_0_25008.c:11: error: `a' undeclared (first use in this function)
61613_0_25008.c:11: error: (Each undeclared identifier is reported only once
61613_0_25008.c:11: error: for each function it appears in.)
61613_0_25008.c: In function `work':
61613_0_25008.c:35: error: syntax error before '{' token
61613_0_25008.c: At top level:
61613_0_25008.c:40: error: syntax error before '}' token