GW-BASIC : Simultaneous Equations Solver

[kimpro82]

• Code (successful)

  10  ' Subject : Simultaneous Equations Solver
  20  ' Author  : kimpro82
  30  ' Date    : 2024.08.20
  40  '
  50  ' Program Description: This program solves a system of linear equations:
  60  ' ax + by = c
  70  ' dx + ey = f
  80  ' The user inputs the coefficients a, b, c, d, e, f. If no input is provided, random values are generated.
  90  ' The solution for x and y is calculated and displayed. Enter Q or q to quit.
  
  100 ' Initialize and get input data
  110 DIM COEF#(5) ' Array to store coefficients
  120 PRINT "The system of equations is:"
  130 PRINT "  ax + by = c"
  140 PRINT "  dx + ey = f"
  
  150 PRINT "Enter coefficients a, b, c, d, e, f (separated by spaces), or Q/q to quit:"
  160 INPUT INPUTDATA$ ' Get user input
  
  200 ' Check for quit command or process input
  210 IF INPUTDATA$ = "Q" OR INPUTDATA$ = "q" THEN GOTO 900
  220 ' GOSUB 800 ' Initialize variables; Not use
  230 GOSUB 300 ' Process input or generate random values
  240 GOSUB 500 ' Solve the equations
  250 GOTO 150
  
  300 ' Parse input or use default values
  310 INPUTDATA$ = INPUTDATA$ + " 0 0 0 0 0 0"  ' Pad the input with zeros if fewer than 6 values are provided
  320 INDEX = 1
  330 FOR I = 0 TO 5
  340   WORD$ = ""
  350   CONDITION = 1
  360   WHILE CONDITION
  370     CHAR$ = MID$(INPUTDATA$, INDEX, 1)
  380     IF CHAR$ <> " " THEN WORD$ = WORD$ + CHAR$ ELSE CONDITION = 0
  390     ' PRINT "I:"; I; "/ INDEX:"; INDEX; "/ CHAR:"; CHAR$; " / WORD:"; WORD$; " / CONDITION:"; CONDITION ' Debug print
  400     INDEX = INDEX + 1
  410   WEND
  420   COEF#(I) = VAL(WORD$)
  430 NEXT I
  450 RETURN
  
  500 ' Solve the system of linear equations
  510 A = COEF#(0): B = COEF#(1): C = COEF#(2)
  520 D = COEF#(3): E = COEF#(4): F = COEF#(5)
  530 PRINT "The equations you entered are:"
  540 PRINT "  "; A; "x +"; B; "y ="; C
  550 PRINT "  "; D; "x +"; E; "y ="; F
  560 DETERMINANT = A * E - B * D
  
  600 IF DETERMINANT = 0 THEN PRINT "The system has no unique solution."
  610 IF DETERMINANT <> 0 THEN X = (C * E - B * F) / DETERMINANT
  620 IF DETERMINANT <> 0 THEN Y = (A * F - C * D) / DETERMINANT
  630 IF DETERMINANT <> 0 THEN PRINT "Solution: x = "; X; ", y = "; Y
  640 ' It is crazy to handle IF conditions in GW-BASIC!
  650 RETURN
  
  800 ' Initialize variables; Not use
  810 ' FOR I = 0 TO 5
  820 '   COEF#(I) = 0 ' Set all coefficients to 0
  830 ' NEXT I
  840 ' RETURN
  
  900 ' Quit the program
  910 PRINT "Program terminated."
  920 END