View Compilation Error

0_0_27828313_7630.c: In function 'main':
0_0_27828313_7630.c:6:1: error: 'sum' undeclared (first use in this function)
 sum=0;
 ^
0_0_27828313_7630.c:6:1: note: each undeclared identifier is reported only once for each function it appears in
0_0_27828313_7630.c:7:1: error: 'for' loop initial declarations are only allowed in C99 or C11 mode
 for(int x=1;x<=y;x++)
 ^
0_0_27828313_7630.c:7:1: note: use option -std=c99, -std=gnu99, -std=c11 or -std=gnu11 to compile your code