Programming

!*************************************************  *********************
!                                                                      *
!                                projectile question                        *
!                                                                      *
!*************************************************  **********************

      
             DATA M,G,C/10.0,9.80665,0.1/
      
	!FIRST i HAVE REDUCED THE GIVEN EQUATION IN TWO LINEAR 1ST-ORDER EQUATIONS
	!FOR THE SOLUTION TO PROCEED
        

      F1(T,U1,Y2) = U1
      F2(T,U1,Y2) = (-M*G-C*U1**2)/M


	!ASSIGNMENT OF VALUES TO CONSTANTS
	
        
      
            WRITE(*,*) 'Input left and right endpoints separated by'
            WRITE(*,*) 'blank'
            WRITE(*,*) ' '
            READ(*,*) A, B
            
         WRITE(*,*) 'Input the two initial conditions.'
         WRITE(*,*) ' '
         READ(*,*) ALPHA1, ALPHA2
          
            WRITE(6,*) 'Input a positive integer for the number'
            WRITE(6,*) 'of subintervals '
            WRITE(6,*) ' '
            READ(5,*) N
            
      
      WRITE(*,6)
             6     FORMAT(12X,'t(i)',11X,'w1(i)',11X,'w2(i)')
           
      H=(B-A)/N
      T=A


   ! the initiaal conditions
      W1=ALPHA1
      W2=ALPHA2

      WRITE(*,1) T,W1,W2

	!RK PARAMETER EVALUATIONS HERE

      DO 110 I=1,N

         X11=H*F1(T,W1,W2)
         X12=H*F2(T,W1,W2)

         X21=H*F1(T+H/2,W1+X11/2,W2+X12/2)
         X22=H*F2(T+H/2,W1+X11/2,W2+X12/2)

         X31=H*F1(T+H/2,W1+X21/2,W2+X22/2)
         X32=H*F2(T+H/2,W1+X21/2,W2+X22/2)

         X41=H*F1(T+H,W1+X31,W2+X32)
         X42=H*F2(T+H,W1+X31,W2+X32)

         W1=W1+(X11+2*X21+2*X31+X41)/6
         W2=W2+(X12+2*X22+2*X32+X42)/6

         T=A+I*H

         WRITE(*,1) T,W1,W2
       110      CONTINUE

        
      STOP
          1     FORMAT(3(1X,E15.8))
      END

// pseudo-code 
ymax  = 0
tymax = 0
t        = 0
yt      = 0
while (yt >=0 ) do
    // compute y(t) at t+dt using RK-4 for instance
    if yt > ymax then 
        ymax  = yt
        tymax = t 
    endif
    t+=dt
end while