September 2017 Update

Task/Loops-Downward-for/EDSAC-order-code/loops-downward-for.edsac

@@ -0,0 +1,54 @@
+[ Loop with downward counter
+  ==========================
+
+  A program for the EDSAC
+
+  Prints the integers 10 down to 0
+
+  The counter is stored at address 20@
+
+  Its initial value is 9 * 2^12
+  (9 in the high 5 bits, representing
+  the character '9') and it counts
+  down in steps of 2^12
+
+  Works with Initial Orders 2 ]
+
+        T56K    [ set load point ]
+        GK      [ set base address ]
+
+[ orders ]
+
+        O14@    [ print figure shift ]
+        O15@    [ print '1' ]
+        O16@    [ print '0' ]
+        O17@    [ print CR ]
+        O18@    [ print LF ]
+
+[ 5 ]   O20@    [ print c ]
+        O17@    [ print CR ]
+        O18@    [ print LF ]
+
+        T19@    [ acc := 0 ]
+        A20@    [ acc += c ]
+        S15@    [ acc -:= character '1' ]
+        U20@    [ c := acc ]
+
+        E5@     [ branch on non-negative ]
+
+        ZF      [ stop ]
+
+[ constants ]
+
+[ 14 ]  #F      [ πF -- figure shift ]
+[ 15 ]  QF      [ character '1' ]
+[ 16 ]  PF      [ character '0' ]
+[ 17 ]  @F      [ θF -- CR ]
+[ 18 ]  &F      [ ΔF -- LF ]
+
+[ variables ]
+
+[ 19 ]  P0F     [ used to clear acc ]
+[ 20 ]  OF      [ character c = '9' ]
+
+        EZPF    [ start when loaded ]