Start to CodeInstructor: Xiao Liu

IntroductionXiao Liu

Third-year Ph.D. Candidate

@ Information Sciences and Technology

Penn State University, University Park

Research Interests:

Programming Languages

Software Engineering & Security

Why coding?

Applications

Today● Course Info● What does a computer do● Turing Machine

Course Information● Basics about Programming

○ Statement○ Branching○ Loop○ Functions

● Computational Thinking○ Sorting○ Searching○ Parallel Processing

● Programming an Artifact○ Design & Implementation○ Testing & Debugging○ Summarization

What does a Computer do● Fundamentally

○ Calculation - Moore’s Law■ Double every 18 months

What does a Computer do● Fundamentally

○ Calculation - Moore’s Law■ Double every 18 months■ 10,000,000,000 cal/sec

What does a Computer do● Fundamentally

○ Calculation - Moore’s Law■ Double every 18 months■ 10,000,000,000 cal/sec

1 + 2 - 10 + 11 + 7 - 6 - 4 + 22 - 1

What does a Computer do● Fundamentally

○ Calculation - Moore’s Law○ Storage - Different levels

What does a Computer do● Fundamentally

○ Calculation - Moore’s Law○ Storage - Different levels

■ Register■ Cache■ Memory■ Hard Disk

What does a Computer do● Fundamentally

○ Calculation - Moore’s Law○ Storage - Different levels

■ Register - 32 bits 00000000111111110000000011111111■ Cache ■ Memory■ Hard Disk

What does a Computer do● Fundamentally

○ Calculation - Moore’s Law○ Storage - Different levels

■ Register - 32 bits 00000000111111110000000011111111■ Cache - 256 KB (65,536 * size of Register)■ Memory ■ Hard Disk

What does a Computer do● Fundamentally

○ Calculation - Moore’s Law○ Storage - Different levels

■ Register - 32 bits 00000000111111110000000011111111■ Cache - 256 KB (65,536 * size of Register)■ Memory - 8 MB (32 * size of Cache)■ Hard Disk - 256 GB (32,768 * size of Memory)

What does a Computer do● Fundamentally

○ Calculation - Moore’s Law○ Storage - Different levels

■ Register - 32 bits 00000000111111110000000011111111■ Cache - 256 KB (65,536 * size of Register)■ Memory - 8 MB (32 * size of Cache)■ Hard Disk - 256 GB (32,768 * size of Memory)

Size Increase

What does a Computer do● Fundamentally

○ Calculation - Moore’s Law○ Storage - Different levels

■ Register - 32 bits 00000000111111110000000011111111■ Cache - 256 KB (65,536 * size of Register)■ Memory - 8 MB (32 * size of Cache)■ Hard Disk - 256 GB (32,768 * size of Memory)

Why not store everything in Hard Disk?

What does a Computer do● Fundamentally

○ Calculation - Moore’s Law○ Storage - Different levels

■ Register - 1 CPU clock cycle, 2 GHz, 2,000,000,000 access/sec ■ Cache - ?■ Memory - ?■ Hard Disk - ?

What does a Computer do● Fundamentally

○ Calculation - Moore’s Law○ Storage - Different levels

■ Register - 1 CPU clock cycle, 2 GHz, 2,000,000,000 access/sec ■ Cache - 100 GB/second ■ Memory - 10 GB/sec ■ Hard Disk - 2000 MB/second

Speed Increase

What does a Computer do● Fundamentally

○ Calculation - Moore’s Law○ Storage - Different levels

● What kind of calculations?

What does a Computer do● Fundamentally

○ Calculation - Moore’s Law○ Storage - Different levels

● What kind of calculations?○ +, - , *, /○ Any more?

What does a Computer do● Fundamentally

○ Calculation - Moore’s Law○ Storage - Different levels

● What kind of calculations?○ +, - , *, /○ Turing Machine - Most General Model about Computing

Alan Turing (1912-1954)

What does a Computer do● Fundamentally

○ Calculation - Moore’s Law○ Storage - Different levels

● What kind of calculations?○ +, - , *, /○ Turing Machine

■ Read the symbol on the square under the head.■ Edit the symbol by writing a new symbol or erasing it.■ Move the tape left of right by one square so that the machine can read and edit the

symbol on a neighbouring square.

What does a Computer do● Fundamentally

○ Calculation - Moore’s Law○ Storage - Different levels

● What kind of calculations?○ +, - , *, /○ Turing Machine

Symbol read Write instruction Move instructionBlank None None0 Write 1 Move tape to the right1 Write 0 Move tape to the right

The current symbol under the head is 0, so we write a 1 and move the tape right by one square.

What does a Computer do● Fundamentally

○ Calculation - Moore’s Law○ Storage - Different levels

● What kind of calculations?○ +, - , *, /○ Turing Machine

Symbol read Write instruction Move instructionBlank None None0 Write 1 Move tape to the right1 Write 0 Move tape to the right

The symbol being read is now 1, so we write a 0 and move the tape right by one square:

What does a Computer do● Fundamentally

○ Calculation - Moore’s Law○ Storage - Different levels

● What kind of calculations?○ +, - , *, /○ Turing Machine

Symbol read Write instruction Move instructionBlank None None0 Write 1 Move tape to the right1 Write 0 Move tape to the right

Similarly, the symbol read is a 1, so we repeat the same instructions.

What does a Computer do● Fundamentally

○ Calculation - Moore’s Law○ Storage - Different levels

● What kind of calculations?○ +, - , *, /○ Turing Machine

Symbol read Write instruction Move instructionBlank None None0 Write 1 Move tape to the right1 Write 0 Move tape to the right

Similarly, the symbol read is a 1, so we repeat the same instructions.

Lab 1: Try A Turing Simulatorhttps://turingmachinesimulator.com/

Even Number of Zeros

q0, 0q1, 0, >

Current State

Symbol Read

Next State

Symbol Write

Move

Lab 1: Try A Turing SimulatorHow to modify this into

Odd Number of Zeros?