Computer Programming

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1 Computer Programming Dr. Deepak B Phatak Dr. Supratik Chakraborty Department of Computer Science and Engineering Session: Computer Architecture Dr. Deepak B. Phatak & Dr. Supratik Chakraborty, 1

2 Quick Recap of Relevant Topics Dumbo model of computing Named drawers for storing/retrieving values Workbench registers for computing Input and output using carts 2 Dr. Deepak B. Phatak & Dr. Supratik Chakraborty,

3 Overview of This Lecture What is it that we will actually be programming From Dumbo to a real computer (almost a Dumbo!) Simplified architecture of a computer Functionalities of different parts Bits and bytes of information 3 Dr. Deepak B. Phatak & Dr. Supratik Chakraborty,

4 Main Memory A Simple Real Computer Dumbo s Drawers Dumbo s Cart Dumbo s Cart Location 0 Location 1 Location 2 Dumbo s Cart Address Data Dumbo s Workbench Register 0 Register 1 Register 2 Register 3 Controller Arithmetic and Logical Unit (ALU) Central Processing Unit (CPU) BUS Disk Output Device Input Device Dr. Deepak B. Phatak & Dr. Supratik Chakraborty, 4

5 Main Memory Parts of a Computer Location 0 Location 1 Location 2 Address Data Register 0 Register 1 Register 2 Register 3 Arithmetic and Logical Unit (ALU) Controller Central Processing Unit (CPU) BUS Disk Output Device Input Device Dr. Deepak B. Phatak & Dr. Supratik Chakraborty, 5

6 Main Memory Usually called Random Access Memory (RAM) or simply Memory Large number of addressable locations Each location stores exactly one value at a time Even if you don t store a value at a location, garbage value exists Writing to a location destroys value originally there Reading a location makes a copy, does not destroy value Dr. Deepak B. Phatak & Dr. Supratik Chakraborty, 6

7 Main Memory Parts of a Computer Location 0 Location 1 Location 2 Address Data Register 0 Register 1 Register 2 Register 3 Arithmetic and Logical Unit (ALU) Controller Central Processing Unit (CPU) BUS Disk Output Device Input Device Dr. Deepak B. Phatak & Dr. Supratik Chakraborty, 7

8 Registers Much faster, costlier and smaller than main memory Won t see much of these in our programs Works behind the scenes Advanced programming can refer to registers directly We won t get to cover this in this course Dr. Deepak B. Phatak & Dr. Supratik Chakraborty, 8

9 Main Memory Parts of a Computer Location 0 Location 1 Location 2 Address Data Register 0 Register 1 Register 2 Register 3 Arithmetic and Logical Unit (ALU) Controller Central Processing Unit (CPU) BUS Disk Output Device Input Device Dr. Deepak B. Phatak & Dr. Supratik Chakraborty, 9

10 ALU and Controller Arithmetic Logic Unit (ALU) Workhorse of computer All arithmetic (add, multiply ) and logical (and, or ) operations happen here Takes operands from registers, stores result in registers Controller Sequences various actions involved in executing instructions Dr. Deepak B. Phatak & Dr. Supratik Chakraborty, 10

11 Main Memory Parts of a Computer Location 0 Location 1 Location 2 Address Data Register 0 Register 1 Register 2 Register 3 Arithmetic and Logical Unit (ALU) Controller Central Processing Unit (CPU) BUS Disk Output Device Input Device Dr. Deepak B. Phatak & Dr. Supratik Chakraborty, 11

12 Disks and Input/Output Devices Disks Longer term storage for files (programs, data, logs, outputs ) Like main memory, but much slower, larger, cheaper More later when we study about files Input/Output (aka I/O) Devices Allows computer to interact with world outside Input device: Keyboard for us Output device: Console (screen) for us Computers can interact with other kinds of I/O devices too! Dr. Deepak B. Phatak & Dr. Supratik Chakraborty, 12

13 Main Memory Parts of a Computer Location 0 Location 1 Location 2 Address Data Register 0 Register 1 Register 2 Register 3 Arithmetic and Logical Unit (ALU) Controller Central Processing Unit (CPU) BUS Disk Output Device Input Device Dr. Deepak B. Phatak & Dr. Supratik Chakraborty, 13

14 Buses Highways for transfering information between different parts Address bus, data bus, I/O bus, external device bus (Universal Serial Bus) We won t see these in our study Works behind the scenes Dr. Deepak B. Phatak & Dr. Supratik Chakraborty, 14

15 Main Memory How is Information Represented? All information represented as sequences of 0 s and 1 s Snapshot: Address Data CPU BUS Dr. Deepak B. Phatak & Dr. Supratik Chakraborty, 15

16 Internal Representation of Information Electronic circuits in a computer can efficiently store and process two states of electrical signals Call them 0 and 1 Information represented using 0 and 1 Binary representation 0 and 1 called bits (binary digits) Information accessed in chunks of 8 bits: a byte Memory access, I/O access, register access, addresses, Important to understand how numbers, characters, strings are represented using bits and bytes Topic of another lecture Dr. Deepak B. Phatak & Dr. Supratik Chakraborty, 16

17 Summary Architecture of a simple real computer Main memory Registers ALU Input/Output devices Disk Bus Representing information: Bits and bytes Dr. Deepak B. Phatak & Dr. Supratik Chakraborty, 17

Computer Programming

Computer Programming Dr. Deepak B Phatak Dr. Supratik Chakraborty Department of Computer Science and Engineering Session: Introduction to Pointers Part 1 Dr. Deepak B. Phatak & Dr. Supratik Chakraborty,