Notes from all lectures about binary numbers, operating systems, object-oriented programming (OOP), data types and algorithms (insertion sort, bubble sort, sequential search, binary search). Important concepts are marked in bold, other terms are underlined.
To convert text into binary language, we use bytes. Characters like A-Z, a-z, 0-9 and
special characters must be encoded into specific binary chains. For this, we need to encode
about 100 symbols, which means we need at least 7 bits (2^7 = 128 ≥ 100). The standard
is to use 8 bits (= 1 byte).
• A byte is in fact one row of the RAM memory. A kilobyte is 1024 = 2^10 (≈ 10^3 ≈
1000) bytes
3. General structure of a computer
A computer consists of a Central Processing Unit (CPU), Memory Unit, and Input/Output (I/O)
devices.
The CPU interacts with memory unit. It consists of:
• Control Unit (CU): Manages machine cycle. Fetches next instruction from program counter
→ decodes information from instruction register
→ informs ALU to execute action
• Arithmetic/Logic unit (ALU): generates ‘new’ data
by doing calculations and computations. ALU is
comprised of logic gates (see Lecture 1)
• clock: Syncs busses
◦clock rate = machine cycles per second. A
higher clock rate means more instructions
per second → faster computer
, • registers: small memory unit (collection of flip-flops, usually 32-bit or 64-bit) within the
CPU for speed. Can serve a general or special purpose.
◦general: It holds data for ALU and stores its output (general purpose)
◦special: It holds instructions
‣ programm counter: adress to next instruction
‣ instruction register: current instruction to be executed
It is essentially a collection of transistors: electric semiconductors to amplify signals to
enable of disable.
In the RAM memory unit, logic gates are used in a transistor circuit (flip-flop) to store
information. It temporarily holds the data the processor just acted on or will act on soon.
Each row in memory is always 1 byte (= 8 bits). Also sequential instructions are stored here,
so that the CPU can immediately access them when the users opens a program. Each
memory cell has a value (8 bits) and an address. The more bits are in an adress, the
more rows of information can be stored: x bits means 2^x locations.
• For a 4GB RAM memory, you need an address of 32 bits: 4*2^30 = 2^2 * 2^30 = 2^32
• Long term holding of data is done in the storage (ROM). This belongs to the I/O unit.
It is not made of transistors, because it should hold data even when power is shut down
(non-volatile)
Input unit: to enter data into the computer (keyboard, mouse)
Output unit: to store information on a harddrive, or to show it on a monitor/screen
Data transfer goes through wires:
• data bus (information): bi-directional from and to CPU
• address bus (where should it go): memory address is put on address bus
• control bus (things that need to be processed to CPU): signals control transfer of data,
read/write request, complete transfer
Basic computer operations:
• receiving data/input
• storing data in memory
• performing mathematical and textual manipulations
• Comparing contents of two memory locations and choosing one (OR-logic)
• Repeating a group of operations (for- and while-loops)
• Executing information, processing data/output
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