Introduction to Programming

The Infinite Java Training

René Schwietzke, Xceptance

Introduction

This will be more than just Java.

• Learn the x86 architecture basics
• Learn programming basics
• Learn Java and OOP
• ... and more.

If you don't know how the basics work, you don't understand how a programming language works.

License

This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

c b a

http://creativecommons.org/licenses/by-sa/4.0/

Programming

The Classic Way to Write Programs

Programming

The most basic way to write a program.

# Machine Code
b8    21 0a 00 00   #moving "!\n" into eax
a3    0c 10 00 06   #moving eax into first memory location
b8    6f 72 6c 64   #moving "orld" into eax
a3    08 10 00 06   #moving eax into next memory location
b8    6f 2c 20 57   #moving "o, W" into eax
a3    04 10 00 06   #moving eax into next memory location
b8    48 65 6c 6c   #moving "Hell" into eax
a3    00 10 00 06   #moving eax into next memory location
b9    00 10 00 06   #moving pointer to start of memory location into ecx
ba    10 00 00 00   #moving string size into edx
bb    01 00 00 00   #moving "stdout" number to ebx
b8    04 00 00 00   #moving "print out" syscall number to eax
cd    80            #calling the linux kernel to execute our print to stdout
b8    01 00 00 00   #moving "sys_exit" call number to eax
cd    80            #executing it via linux sys_call

; Assembler

section     .text
global      _start                      ;must be declared for linker (ld)

_start:                                 ;tell linker entry point

    mov     edx,len                     ;message length
    mov     ecx,msg                     ;message to write
    mov     ebx,1                       ;file descriptor (stdout)
    mov     eax,4                       ;system call number (sys_write)
    int     0x80                        ;call kernel

    mov     eax,1                       ;system call number (sys_exit)
    int     0x80                        ;call kernel

section     .data

msg     db  'Hello, world!',0xa         ;our dear string
len     equ $ - msg                     ;length of our dear string

Even Assembler is a programming language despite its basic syntax.

A Piece of Linux

A few kernel lines...

/**
 * frame_vector_to_pfns - convert frame vector to contain pfns
 * @vec:	frame vector to convert
 *
 * Convert @vec to contain array of pfns.
 */
void frame_vector_to_pfns(struct frame_vector *vec)
{
	int i;
	unsigned long *nums;
	struct page **pages;

	if (vec->is_pfns)
		return;
	pages = (struct page **)(vec->ptrs);
	nums = (unsigned long *)pages;
	for (i = 0; i < vec->nr_frames; i++)
		nums[i] = page_to_pfn(pages[i]);
	vec->is_pfns = true;
}

Kind of strange that this all works...

High-Level Languages

Just a quick overview

https://en.wikipedia.org/wiki/High-level_programming_language

Language Examples

// Java
class HelloWorld {
    public static void main( String args[] ) {
        System.out.println( "Hello World!" );
    }
}

// Kotlin
fun main(args : Array<String>) {
    println("Hello, world!")
}

// Scala
object HelloWorld extends App {
    println("Hello world!")
}

# Perl
print "Hello World!\n";

// C++
#include <iostream>

int main() {
    std::cout << "Hello World!" << std::endl;
}

// JavaScript
console.log("Hello World");

// C#
class HelloWorld {
    static void Main() {
        System.Console.WriteLine("Hello, World!");
    }
}

// Ceylon
print("Hello, World!");

// Go
package main

import "fmt"

func main() {
    fmt.Printf("Hello World\n")
}

# Python
print("Hello World")

Just a few out of 500+.