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1 Data Types What is a Data type? A Data type defines how a pattern of bits will be interpreted. What are Intrinsic Data types? Intrinsic data types are the data types that are defined within a particular programming language. There are numerous different data types. They are used to make the storage and processing of data easier and more efficient. Different databases and programming systems have their own set of intrinsic data types, but the main ones are: Integer Real Boolean String Character Date Container Integer:- An integer is a positive or negative number that is stored as a whole. (i.e it does not have a fractional part).integers are held in pure binary for processing and storage. Most programming languages differentiate between short integers and long integers. Obviously more bytes are used to store long integers. Real:- A real number is any positive or negative number. This includes all integers and all rational and irrational numbers. Rational numbers may be expressed as a fraction (such as 7/8) and irrational numbers may be expressed by an infinite decimal representation ( ). Real numbers that include decimal points are also called floating point numbers, since the decimal "floats" between the digits. Boolean:- A Boolean is a data-type that can store one of only two values usually these values are True or False. Booleans are stored in one byte True being stored as False as String:- A string is a data type used in programming, such as an integer and floating point unit, but is used to represent text rather than numbers. It is comprised of a set of characters that can also contain spaces and numbers. For example, the word "hamburger" and the phrase "I ate 3 hamburgers" are both strings. Even "12345" could be considered a string, if specified correctly. Typically, programmers must enclose strings in quotation marks for the data to recognize as a string and not a number or variable name.each character within a string will be stored in one byte using its ASCII code; modern systems might store each character in two bytes using its Unicode. The maximum length of a string is limited only by the available memory. Character:- A character is any letter, number, space, punctuation mark, or symbol that can be typed on a computer.

2 The word "computer," for example, consists of eight characters. The phrase "Hi there." takes up nine characters. Each character requires one byte of space, so "computer" takes up 8 bytes. The list of characters that can be typed is defined by the ASCII and extended ASCII set. Dates:- Dates In most computer systems dates are stored as a serial number that equates to the number of seconds since January 1st, 1904 (thus they also contain the time). Although the serial numbers are used for processing purposes, the results are usually presented in one of several standard date formats. For example, dd/mm/yyyy, or dd MonthName, yyyy. Dates usually take 8 bytes of storage Container Files:- In computer science, a container is a class, a data structure or an abstract data type (ADT) whose instances are collections of other objects. In other words, they store objects in an organized way that follows specific access rules. A container is a data-type used for storing images, video, sound or another type of complex file. Note that in MySQL databases the term blob (binary large object) is used rather than container Comparison of the common data types:- Estimating the Size of a File:- Basically we will need the following formula:- Size of file = ([size of each record] * [number of records]) +[additional space] Consider a record that stores the following data:- STUDENT(AdminNumber, Name, PostCode, Telephone, DoA, Age) Attribute Data Type Data Example (Extreme Data) AdminNumber Integer Name String Hassan Zulfiqar Haider 25 PostCode String Telephone String (042) DOA Date Age Real 18 4 TOTAL 62 Size of Data (Bytes)

3 So 200 records will take:- ASCII Character Sets:- The 104-key PC US English QWERTY keyboard layout evolved from the standard typewriter keyboard, with extra keys for computing. ASCII normally uses 8 bits (1 byte) to store each character. However, the 8th bit is used as a check digit, meaning that only 7 bits are available to store each character. This gives ASCII the ability to store a total of 128 different values. (2^7). ASCII values can take many forms: Numbers Letters (capitals and lower case are separate) Punctuation (?/ \ $ etc.) non-printing commands (enter, escape, F1) Take a look at your keyboard and see how many different keys you have. The number should be 104 for a windows keyboard, or 101 for traditional keyboard. With the shift function values (a, A; b, B etc.) and recognising that some keys have repeated functionality (two shift keys, the num pad). We roughly have 128 functions that a keyboard can perform.

4 Unicode:- The problem with ASCII is that it only allows you to represent a small number of characters (~128 or 256 for Extended ASCII). This might be OK if you are living in an English speaking country, but what happens if you live in a country that uses a different character set?

5 You can see that we quickly run into trouble as ASCII can't possibly store these hundreds of thousands of extra characters in just 7 bits. What we do instead is use unicode. There are several versions of unicode, each with using a different number of bits to store data: UTF 8 In UTF-8, every code point from is stored in a single bytes. Only code points 128 and above are stored using 2,3 or in fact, up to 4 bytes. In short, UTF-8 is variable length encoding and takes 1 to 4 bytes, depending upon code point. UTF 16 UTF-16 is also variable length character encoding but either takes 2 or 4 bytes. UTF 32 On the other hand UTF-32 is fixed 4 bytes.