; Play Conway's Game of Life on a monochrome ST. This program was ; developed with the AssemPro assembler from Abacus Software. ; ; Designed and programmed by Eric Bergman-Terrell, 1987 ; ; Press left mouse button to quit the program. ; Press right mouse button to get a new cell generation. text ilabel c:\assemble\tos\tos.l ; Total x-pixels total_x_pix = 640 ; Total y-pixels total_y_pix = 400 ; Width of rectangle pix_x_len = 4 ; Height of rectangle pix_y_len = 4 ; Pixels in y-dimension x_pixels = (total_x_pix / pix_x_len) * pix_x_len ; Pixels in x-dimension y_pixels = (total_y_pix / pix_y_len) * pix_y_len ; Cells in x-dimension x_cells = x_pixels / pix_x_len ; Cells in y-dimension y_cells = y_pixels / pix_y_len ; Total number of cells total_cells = x_cells * y_cells start: gem_init ; Get a local stack for use by this program. lea stack_top, sp bsr init_gr ; Make the first generation of cells. restart: bsr randomize bsr init_old ; Plot the current generation to the screen. loop_2: bsr plot bsr new_to_old ; Produce the next generation. bsr update ; If right mouse button is pressed, quit. ; If left mouse button is pressed, create a new ; random generation. vq_mouse gr_handle, d0, d1, d2 and.w #3, d0 beq.s loop_2 and.w #1, d0 beq.s restart quit: gem_exit rts ; Copy new generation into old generation new_to_old: lea oldgen, a0 lea newgen, a1 move.w #(total_cells / 2 - 1), d0 ; d0 holds number of ; longwords to copy. assign_lp: move.w (a1)+, (a0)+ dbf d0, assign_lp rts ; Give the old generation an initial value totally different than ; the initial value of the new generation. init_old: lea oldgen, a0 move.w #(total_cells / 2 - 1), d1 ; d1 holds number of ; longwords to set. move.w #$0202, d0 init_lp: move.w d0, (a0)+ dbf d1, init_lp rts ; Produce a new generation of cells. For each nonempty cell, if it ; has two or three neighbors, it survives, otherwise it dies. If an ; empty cell has three neighbors, it becomes nonempty. A cell can ; have up to eight neighbors: ; ; ------- ; |N|N|N| ; ------- ; |N|*|N| * denotes a cell ; ------- N denotes a cell's neighbors ; |N|N|N| ; ------- ; update: lea oldgen - 1, a0 lea newgen - 1, a1 clr.w d0 ; x-coordinate clr.w d1 ; y-coordinate move.w #(x_cells - 1), d3 ; constant x_cells - 1 move.w #(y_cells - 1), d4 ; constant y_cells - 1 loop_5: addq.l #1, a0 addq.l #1, a1 clr.b d2 ; Compute number of oldgen[x, y]'s ; neighbors. ; Don't compute neighbors of a cell on a border. tst.w d0 beq.s update_cell tst.w d1 beq.s update_cell cmp.w d3, d0 beq.s update_cell cmp.w d4, d1 beq.s update_cell ; Count the neighbors of the current cell. add.b (-x_cells - 1)(a0), d2 add.b (-x_cells )(a0), d2 add.b (-x_cells + 1)(a0), d2 add.b (-1) (a0), d2 add.b (1) (a0), d2 add.b (x_cells - 1) (a0), d2 add.b (x_cells) (a0), d2 add.b (x_cells + 1) (a0), d2 update_cell: tst.b d2 beq.s do_clear tst.b (a0) beq.s empty cmp.b #2, d2 beq.s do_set cmp.b #3, d2 beq.s do_set bra.s do_clear do_set: move.b #1, (a1) bra.s next_x2 do_clear: clr.b (a1) bra.s next_x2 empty: cmp.b #3, d2 beq.s do_set bra.s do_clear next_x2: addq.w #1, d0 cmp.w d3, d0 bgt.s next_y2 bra.s loop_5 next_y2: clr.w d0 addq.w #1, d1 cmp.w d4, d1 bgt.s quit2 bra.s loop_5 quit2: rts ; Prepare to plot to screen. init_gr: vs_clip gr_handle, #1, px vswr_mode gr_handle, #1, d0 vsf_color gr_handle, #1, d0 vsl_color gr_handle, #1, d0 v_hide_c gr_handle ; Make sure that rectangle perimeters are not drawn. vsf_perimeter gr_handle, #0, d0 bsr clear rts ; Clear the screen. clear: vsf_interior gr_handle, #8, d1 lea pxy_array, a3 clr.w (a3)+ clr.w (a3)+ move.w #(total_x_pix - 1), (a3)+ move.w #(total_y_pix - 1), (a3) v_bar gr_handle, pxy_array rts ; Generate a random cell pattern. randomize: lea newgen, a3 move.w #(total_cells - 1), d1 loop: ; Save registers. movem.l d1/a3, -(sp) random ; Restore registers. movem.l (sp)+, d1/a3 move.w d0, d3 and.w #7, d3 asr.b d3, d0 and.l #1, d0 move.b d0, (a3)+ dbf d1, loop ; Remove cells from the border of the rectangle. trim: lea newgen, a3 subq.l #1, a3 clr.w d0 ; x-coordinate clr.w d1 ; y-coordinate move.w #(x_cells - 1), d4 ; constant x_cells - 1 move.w #(y_cells - 1), d5 ; constant y_cells - 1 ; Clear all cells on borders. trim_loop: addq.l #1, a3 tst.w d0 beq.s clear_cell cmp.w d4, d0 beq.s clear_cell tst.w d1 beq.s clear_cell cmp.w d5, d1 beq.s clear_cell next_x_2: addq.w #1, d0 cmp.w d4, d0 bgt.s next_y_2 bra.s trim_loop next_y_2: clr.w d0 addq.w #1, d1 cmp.w d5, d1 bgt.s return_3 bra.s trim_loop return_3: rts ; Remove one cell from a border of the rectangle. clear_cell: clr.b (a3) bra.s next_x_2 ; Plot a cell pattern to the screen. plot: lea newgen, a0 lea oldgen, a1 clr.w d0 ; x-coordinate clr.w d1 ; y-coordinate clr.w d3 draw_loop: move.b (a0), d3 cmpm.b (a0)+, (a1)+ beq next_x ; Draw the rectangle. lea pxy_array, a2 move.w d0, (a2)+ move.w d1, (a2)+ move.w d0, d5 move.w d1, d6 addq.w #(pix_x_len - 1), d5 addq.w #(pix_y_len - 1), d6 move.w d5, (a2)+ move.w d6, (a2) ; Save registers. movem.l d0-d3/a0-a1, -(sp) vsf_interior gr_handle, d3, d2 v_bar gr_handle, pxy_array ; Restore registers. movem.l (sp)+, d0-d3/a0-a1 next_x: addq.w #pix_x_len, d0 cmp.w #x_pixels, d0 bge.s next_y bra draw_loop next_y: clr.w d0 addq.w #pix_y_len, d1 cmp.w #y_pixels, d1 bge.s return_2 bra draw_loop return_2: rts data align px: dc.w 0, 0, total_x_pix, total_y_pix bss align newgen: ds.w total_cells / 2 + 1 oldgen: ds.w total_cells / 2 + 1 pxy_array: ds.w 4 stack_bot: ds.w 512 stack_top: ds.w 0 end