Error(s):

source_file.c: In function ‘main’:
source_file.c:9:1: error: ‘X’ undeclared (first use in this function)
 X=b+c ;
 ^
source_file.c:9:1: note: each undeclared identifier is reported only once for each function it appears in
source_file.c:8:1: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d" ,&x) ;
 ^