Original algorithms were mathematical procedures, example:
Special form of English. Ingredients are the "data".
Special notation:
Automatic execution by a machine:
Program flowchart: Raptor programming language
// sumDown.cpp
// input number, if positive loop summing down to 0. Repeat until 0.
#include <iostream>
using namespace std;
int main () {
int num, sum, i;
do {
cout << "Enter a number: ";
cin >> num;
if (num >= 0) {
sum = 0;
for (i=num; i>0; i--)
sum += i;
cout << "sum=" << sum << endl;
}
} while (num != 0);
}
Same program in Python:
#sumDown.py
#input number, if positive loop summing down to 0. Repeat until 0 is input.
num = eval(input("Enter a number: ")) #first number from user
while num != 0: #until a 0 is entered
if num > 0:
sum = 0
for i in range(num,0,-1): #loop down to zero, adding each number to the sum
sum += i
print("Sum is", sum)
num = eval(input("Enter next number: "))
The above C++ and Python program would be compiled into something similar to the
following program in IBC (Itsy Bitsy Computer) assembly language:
/ program to read number, count down to 0, summing.
/ repeat for positive numbers
Start: In 102 / user input
Load 102,r1 / to r1
Load #0,r0 / 0 to r0
Cmp r1,r0 / compare user's input with 0
Beq done / done if user input a 0
Load #0,r6 / the sum
Load #-1,r2 / the decrement value
Next: Add r1,r6 / r6 += r1
Add r2,r1 / r1--
Store r1,106
Out 106 / display current value
Cmp r0,r1 / =0 yet?
Bne next / if not, loop back to Next
Store r6,108 / but if 0, store sum
Out 108 / display sum
Jmp start / do another
Done: Halt
Raptor flowchart language version:
