Initial data commit

Task/Stack/IS-BASIC/stack.basic

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+100 LET N=255 ! Size of stack
+110 NUMERIC STACK(1 TO N)
+120 LET PTR=1
+130 DEF PUSH(X)
+140   IF PTR>N THEN
+150     PRINT "Stack is full.":STOP
+160   ELSE
+170     LET STACK(PTR)=X:LET PTR=PTR+1
+180   END IF
+190 END DEF
+200 DEF POP
+210   IF PTR=1 THEN
+220     PRINT "Stack is empty.":STOP
+230   ELSE
+240     LET PTR=PTR-1:LET POP=STACK(PTR)
+250   END IF
+260 END DEF
+270 DEF EMPTY
+280   LET PTR=1
+290 END DEF
+300 DEF TOP=STACK(PTR-1)
+310 CALL PUSH(3):CALL PUSH(5)
+320 PRINT POP+POP