Stack Up Interpreter

STACKONE = []
STACKTWO = []
LOG = []
A = 0
B = 0
DEPTH = 0
CODE = 0
LINE = 0
TMPCMD = 0
CMD = 0
def Push(stack,number):
    stack.append(number)
def SPop(stack):
    if len(stack) == 0:
            stack.append(0)
    return stack.pop()
def Overflow(num):
    while num > 255:
        num -= 256
    while num < 0:
        num += 256
    return num
import linecache
import os
A = os.getcwd()
print('Choose a Stack Up program file in: ' + A)
CODE = input("File name: ")
CODE = A+"/"+CODE
print(CODE)
while 1 == 1:
    LINE = LINE + 1
    TMPCMD = linecache.getline(CODE, LINE)
    CMD = TMPCMD[0:4]
    if DEPTH == 0:
        if CMD == 'NEW':
            Push(STACKONE,0)
        if CMD == 'CLN':
            A = SPop(STACKONE)
            Push(STACKONE,A)
            Push(STACKONE,A)
        if CMD == 'DEL':
            A = SPop(STACKONE)
        if CMD == 'SWP':
            A = SPop(STACKONE)
            B = SPop(STACKONE)
            Push(STACKONE,A)
            Push(STACKONE,B)
        if CMD == 'INC':
            A = SPop(STACKONE)
            A += 1
            A=Overflow(A)
            Push(STACKONE,A)
        if CMD == 'DEC':
            A = SPop(STACKONE)
            A -= 1
            A=Overflow(A)
            Push(STACKONE,A)
        if CMD == 'ADD':
            A = SPop(STACKONE)
            B = SPop(STACKONE)
            A += B
            A=Overflow(A)
            Push(STACKONE,A)
        if CMD == 'DIF':
            A = SPop(STACKONE)
            B = SPop(STACKONE)
            A -= B
            A=Overflow(A)
            Push(STACKONE,A)
        if CMD == 'PAS':
            A = SPop(STACKONE)
            Push(STACKTWO,A)
        if CMD == 'PSB':
            A = SPop(STACKTWO)
            Push(STACKONE,A)
        if CMD == 'INI':
            A = input("\n# ")
            A=Overflow(A)
            Push(int(A))
        if CMD == 'OUI':
            A = SPop(STACKONE)
            print(A,end="",flush=True)
        if CMD == 'INA':
            A = input("\n> ")
            A=Overflow(A)
            Push(ord(A[0]))
        if CMD == 'OUA':
            A = SPop(STACKONE)
            print(chr(A),end="",flush=True)
        if CMD == 'LOP':
            A = STACKONE[-1]
            if A == 0:
                DEPTH=DEPTH+1
            else:
                Push(LOG,LINE)
        if CMD == 'STP':
            A = STACKONE[-1]
            B = SPop(LOG)
            if A != 0:
                Push(LOG,B)
                LINE = B
        if CMD == 'END':
            break
    else:
        if CMD == 'LOP':
            DEPTH=DEPTH+1
        if CMD == 'STP':
            DEPTH=DEPTH-1
        if CMD == 'END':
            DEPTH=0
            break
print('End of program.')
linecache.clearcache()