View Compilation Error

0_0_34515803_15026.c:3:1: error: expected identifier or '(' before '/' token
 //#define MaxSize 1000
 ^
0_0_34515803_15026.c:3:3: error: stray '#' in program
 //#define MaxSize 1000
   ^
0_0_34515803_15026.c:5:27: error: expected ';', ',' or ')' before '&' token
 int change(char str[],int &length){
                           ^
0_0_34515803_15026.c: In function 'main':
0_0_34515803_15026.c:36:21: error: 'a' undeclared (first use in this function)
  while(scanf("%s%s",a,b)!=EOF){
                     ^
0_0_34515803_15026.c:36:21: note: each undeclared identifier is reported only once for each function it appears in
0_0_34515803_15026.c:36:23: error: 'b' undeclared (first use in this function)
  while(scanf("%s%s",a,b)!=EOF){
                       ^