Computer Systems Hardware ▫The Physical Machine Software ▫Set of programs Set of instructions
Hardware and Memory Central Processing Unit (CPU) ▫Also known as the Processor ▫Device that performs the instructions in a program ▫Example Intel Core i7
Hardware and Memory Memory ▫Holds data for the computer to process ▫Two forms Main Memory Volatile Example - RAM Auxiliary Memory Non-volatile Example – Hard drive
Bits, Bytes & Address Bit = Binary Digit (0,1) Byte = groups of bits ▫1 Byte = 8 Bits ▫Byte is the smallest addressable unit of memory Address ▫Main memory consists of a long list of numbered bytes ▫The number of a byte in memory is called an Address
Memory Locations 1 byte is not large enough to store all kinds of data Data can be stored in several adjacent bytes These adjacent bytes are considered a single Memory Location Address of the Memory Location ▫Address of the first byte
Operating Systems A program that supervises a computer’s operation Examples ▫Windows XP/7/8 ▫UNIX ▫Linux, Ubuntu ▫Mac OS X
Programming Languages High Level Languages ▫Java, C, C++, C#, Visual Basic, Python Low Level Languages ▫Assembly Language ▫Machine Language
Compilers A Translator Translates from High Level Language to Low Level Language Source code -> Object Code Compile Once, Execute Often
Interpreters Translator + Executor Alternates between translation & execution Translates every time Interpreted programs are slower than compiled ones
Java Bytecode An intermediate language for Java A compiler translated Java code into Bytecode Java Virtual Machine (JVM) ▫Translator to translate & execute Java Bytecode Bytecode runs in any computer that has JVM ▫Portability
Algorithms Like a Recipe! A set of directions for solving a problem Often written in Pseudocode ▫Combination of English & Programming Language
Pseudocode Example Algorithm to compute the total cost of a list of items ▫Write the number o on the whiteboard. ▫For each item on the list Add the cost of the item to the number on the whiteboard Replace the number on the whiteboard with the result of this addition. ▫Announce that the answer is the number written on the whiteboard.
Testing & Debugging Bug ▫A mistake in a program Debugging ▫Process of eliminating mistakes Syntax error ▫Grammatical mistakes Run-time error ▫Error during execution Logic error ▫Conceptual mistakes in algorithm
Software Reuse Java Class Library ▫Java API Example ▫System.out.println
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