prog.c: In function 'RKn':
prog.c:14:29: warning: implicit declaration of function 'malloc' [-Wimplicit-function-declaration]
else if ((k1 = (double*)malloc(5*sizeof(double)*n))==0) return 0;
^
prog.c:14:29: warning: incompatible implicit declaration of built-in function 'malloc'
prog.c:14:29: note: include '<stdlib.h>' or provide a declaration of 'malloc'
prog.c:17:5: warning: implicit declaration of function 'memcpy' [-Wimplicit-function-declaration]
memcpy(X,x,sizeof(double)*n);
^
prog.c:17:5: warning: incompatible implicit declaration of built-in function 'memcpy'
prog.c:17:5: note: include '<string.h>' or provide a declaration of 'memcpy'
prog.c:27:5: warning: implicit declaration of function 'free' [-Wimplicit-function-declaration]
free(k1);
^
prog.c:27:5: warning: incompatible implicit declaration of built-in function 'free'
prog.c:27:5: note: include '<stdlib.h>' or provide a declaration of 'free'
prog.c: In function 'f':
prog.c:36:30: warning: implicit declaration of function 'exp' [-Wimplicit-function-declaration]
Y[0] = -52*x[0]-100*x[1]+exp(-t);
^
prog.c:36:30: warning: incompatible implicit declaration of built-in function 'exp'
prog.c:36:30: note: include '<math.h>' or provide a declaration of 'exp'
prog.c:37:19: warning: implicit declaration of function 'sin' [-Wimplicit-function-declaration]
Y[1] = x[0] + sin(t);
^
prog.c:37:19: warning: incompatible implicit declaration of built-in function 'sin'
prog.c:37:19: note: include '<math.h>' or provide a declaration of 'sin'
/usr/lib/gcc/i586-linux-gnu/5/../../../i386-linux-gnu/crt1.o: In function `_start':
(.text+0x18): undefined reference to `main'
collect2: error: ld returned 1 exit status