Machine Code
It's important to remember (see the notes on What's a Comuter) the computer is a very specific (and complex) arrangement of circuits in such a way that makes it possible for it to remember values and manipulate values (do math), but how does electricity become "values"? That's where Machine Code (often written in binary code) enters the picture. That electrical current is made up of high voltages and low voltages which we refer to as a 1 or a 0 (binary code) for the sake of being able to use these voltages to represent values or data.
As the video above explained, binary code can be used to represent ANY data we choose and we can give the computer data in binary code to operate on, in the old days we would do that by flipping switches (on/off 1/0) or storing our data in punched cards/tape (whole-punch/no-whole-punch 1/0) and having the computer read the tape. We can also pass instructions for what we want the computer to do with the data, computers are designed to (or "wired up to") interpret certain sequences of binary code as instruction codes (like "add" this, or "store" that), and so early programs could look something like this:
click the image to "step" through the program
Programmers rarely ever deal with binary code directly, we made things easier by writnig "assembly code" which were slightly more human readable versions of this machine code (which we would translate into binary before running), here's the same program in a hypothetical assembly language:
ORG 0
LDA A
ADD B
STA C
HLT
A, DEC 84
B, DEC 12
C, DEC 0
END
It's rare you find folks working in assembly these days (though some folks do, check out the cool 8bit art of Rachel Weil for example) becuase if it's that complicated to tell a computer to add 2 numbers together it be virtually impossible to make it do much more complicated tasks (generally speaking, Rachel might disagree). Add to that the fact that you need to know the instruction codes and "architecture" (how the switches are wired up) for every CPU design if you wanted your program to work on every computer (the only computer Rachel worries about is the NES) and you would have to re-write your code each time, essentially you would have to be quite the expert to do even really simple things... enter Grace Hopper:
Programming Languages
This code is an example of FLOW-MATIC the first "english-like" compiled language developed under Admiral Hopper, which would eventually lead to COBOL, which is still used today. It's an obsolete language, but this is as close as I can approximate what it would have looked like to add to numbers together, let's assume the values 84 and 12 are stored in file A and B. Admiral Hopper also popularized the idea of machine-independent programming languages which is generally how we think of programming languages today.
INPUT FIRST FILE=A SECOND FILE=B,
OUTPUT SUM FILE=C;
ADD A TO B
TRANSFER B TO SUM
CLOSE-OUT FILE SUM
STOP.
Today we have lots of "higher level" (of abstraction) languages meant to be written and read by humans. Different languages specialize in different contexts (for example JavaScript is ideal for programming apps for the web) and they all have different "syntax" but ultimately they can all do the same things (JavaScript could be used to write pretty much anything, not just web apps). In order to use a language on any given system (particular computer architecture) you need to make sure someone has written a compiler or interpreter for that language on that system so that your code can get translated to the machine code the computer needs in order to actually run your program. Here are a few more xample of the same simple program written in a few different languages, notice their general similarity despite their difference in syntax
// C
#include <stdio.h>
void main(){
int a = 84;
int b = 12;
int c = a + b;
printf("%d\n", c );
}
// Java
class myprogram
{
public static void main(String args[])
{
int a = 84;
int b = 12;
int c = a + b;
System.out.println(c);
}
}
// JavaScript (aka ECMAScript)
function main(){
var a = 84;
var b = 12;
var c = a + b;
console.log( c );
}
main();
# Python
def main():
a = 84
b = 12
c = a + b
print(c)
main()
<?php # php
function main()
{
$a = 84;
$b = 12;
$c = $a + $b;
echo $c."\n";
}
main();
?>
// C++
#include <iostream>
void main(){
{
int a = 84;
int b = 12;
int c = a + b;
std::cout << c;
}
