Error(s):

710694979/source.c:3:9: error: #include expects "FILENAME" or <FILENAME>
 #include&stdio.h>
         ^
710694979/source.c: In function ‘main’:
710694979/source.c:16:5: warning: implicit declaration of function ‘printf’ [-Wimplicit-function-declaration]
     printf("Enter real and imaginary part of first complex number:\n");
     ^~~~~~
710694979/source.c:16:5: warning: incompatible implicit declaration of built-in function ‘printf’
710694979/source.c:16:5: note: include ‘<stdio.h>’ or provide a declaration of ‘printf’
710694979/source.c:17:5: warning: implicit declaration of function ‘scanf’ [-Wimplicit-function-declaration]
     scanf("%f%f", &cnum1.real, &cnum1.imaginary);
     ^~~~~
710694979/source.c:17:5: warning: incompatible implicit declaration of built-in function ‘scanf’
710694979/source.c:17:5: note: include ‘<stdio.h>’ or provide a declaration of ‘scanf’