Bilgisayarlar kodu nasıl işler? Top-down yaklaşım Modüler yaklaşım

Top down yaklaşım In this scenario, when the code is run the computer starts reading at the top and continues down, going through each line of code until it reaches the end. Old method Fast and easy when code was small and not very complex As the code is processed, it is all loaded into memory

Top down yaklaşım So, the more programs you run, the greater the demands on the system in terms of memory and processor

Top down yaklaşım Also, the bigger the program you are loading, the longer and longer it will take to load up

Top down yaklaşım One is that you have to write code in such a way that it is hard to properly test it until you have finished it. Testing individual parts becomes a nightmare.

Breaking up Code There are huge advantages to coding in this way. The code is broken up into smaller components, so it is easier to write and you can test it earlier and more often. Debugging any code errors is a lot easier because you know what part of the code handles what aspect of the program. You are in a position to reuse certain parts of your code in other projects more easily because they will be self-contained. Building up a big project from smaller, interconnected chunks enables you to build up a project over time and add more features as your skills improve!

Re-usability

Kodun Saklanması (Depolanması) To really make applications usable, you need a way to store the code Storage means that you only have to type or ( more accurately) create the code once, storing it for future access Paper punch cards Magnetic tape reels Magnetic cassettes Floppy disks (5 1/ 4 inch) Floppy disks (3 1/ 2 inch) Hard drives Networked systems CDs DVD Flash drives Internet distribution

Data Data stored as binary

Plain text vs. Compiled The code can be in one of two forms Plain text (Sade metin): Some code that you will come across will be stored and run in the plain text form — JavaScript and VBScript are good examples of this Compiled (Derlenmiş): This is code that has been run through a program called a compiler. The compiler processes the plain-text code and changes it into something called “object code.”

Plain text vs. Compiled Plain text Compiled The main advantage to code stored in plain text is that it is easily read, changes can be made to it easily and quickly, and no special tools are required. No protection! Compiled You can’t look at the compiled code and get back to the source code that way. Therefore protected. You need to keep a copy of the source code in case you need to make any subsequent changes to the code.

Sayı Sistemleri Decimal (Onluk sayı sistemi, On tabanlı) 0 1 2 3 4 5 6 7 8 9 Örnek: 1984 Binary (İkilik sayı sistemi, iki tabanlı) 0 1 Örnek: 10011 Hexadecimal (Onaltılık sayı sistemi) 0 1 2 3 4 5 6 7 8 9 A B C D E F Örnek: 1A2

Onluk Sisteme Dönüşümler Sağdan sola doğru taban değerini hesapla ..., Taban3, Taban2, Taban1, Taban0 Basamak değeri ile taban değerini çarp Çarpımları topla Örnekler: (1984)10 = (?)10 (10011)2 = (?)10 (1A2)16 = (?)10

Onluk Sistemden Dönüşümler Dönüştürülecek tabana bölüm Örnekler: (1984)10 = (?)10 (19)10 = (?)2 (418)10 = (?)16

İkilik sayı sisteminde terimler Bit - 0,1 Nybble – 4 bit Örnek: 1010 Byte – 8 bit Örnek: 10101010 Halfword – 16 bit Örnek: 1010101010101010 Word – 32 bit Örnek: 10101010101010101010101010101010 Doubleword – 64 bit Örnek: 1010101010101010101010101010101010101010101010101010101010101010

Binary ve Hexadecimal arasında dönüşümler 0x3F7D (3F7D)16=(?)2 3 F 7 D 0010 1111 0111 1101 10111101111101 (101111)2=(?)16 0010 1111 2 F 2F

Binary ve Hexadecimal arasında dönüşümler

Sayı sistemlerinde matematik işlemleri Başlat – Programlar – Donatılar – Hesap Makinesi

Bu sinyal ne anlama geliyor? ...---…

Bilgisayarda Alfasayısal Bilginin Temsil Edilmesi ASCII (American Standard Code for Information Interchange) Bilgi Değişimi için Amerikan Standart Kodu

Programming is great! 010100000111001001101111011001110111001001100001011011010110110101101001011011100110011100100000011010010111001100100000011001110111001001100101011000010111010000100001

Why Binary? Tartışma Sorusu: Bilgi işleme sistemlerinde neden ikilik sistemi kullanıyoruz? Neden Onluk sistemi ya da diğer bir sayı sistemini kullanmıyoruz? İki kişilik gruplar halinde tartışınız.