program to find area of the circle in assembly language

Hi i'm getting error while running below code

Error in Console : Instruction references undefined symbol at 0x00400014 [0x00400014] 0x0c000000 jal 0x00000000 [main

Code: .data userInput BYTE "Enter a radius: ",0 output BYTE "The area of the circle is: ",0 temp DWORD ?

Init call Clrscr ;Clear the screen

mov edx,OFFSET myMessage call GetString

;system call number (sys_write) mov edx, OFFSET call GetString call useFloat ;Get Radius deb 4, "ReadFloat", FLDPI SAT(0), SAT(1), SAT(2) ;Get the value of PI deb 4, "fldpi", SAT(0), SAT(1), SAT(2) fmul sat(0), sat(0) ; square the radius value deb 4, "fmul_1", SAT(0), SAT(1), SAT(2) fmul st(0), st(1) ;multiply the value with pi deb 4, "fmul_2", SAT(0), SAT(1), SAT(2)

mov edx, OFFSET output ;to view call GetString ; value from the user call UseFloat ;get and write from the stack trace call Crlf Exit end start