CMPUT 201 Notes

Disclaimer

This course by the U of A was taken during the 2020 quarantine and therefore may not be a true representation of a normal 201 class. People from previous years have claimed that topics such as dp (dynamic programming), greedy, graphs, and others were explored but Dr. Lin Guo-Hui did not really explore these topics.

General

This course is an intro to C. From pointers to make files, this course will develop an intuition for c programming (C++ is almost not taught, for C++ take 275).

Course difficulty: Easy-medium

Summary

Week 1

Setting up up, ie, ssh into server, linux commands etc

# linux commands 
~ # home directory
mkdir cmput201 # make directory
cd cmput201 # change directory
mkdir Week01 # make dir called Week01
pwd # print working dir
ls ~ # list contents of home 
man ls # manual page of ls command
vi celsius.c # create a new or open an existing file in vi

Inline comments with // or /* Some comments */ for block comments

Compiling with gcc -Wall -std=c99

Recommended editor of vim or emacs on the school machine via ssh through Putty but from my experience, WSL2 with vs code will have the same results as the school machines

Week 2

printf and scanf

Escape sequences: ie \n for new line

int and float binary representation

• int - just dec to binary form
• float - converted via IEEE 754 standard

operators and precedence:

In order of highest priority to lowest (if on same level then left to right)

	associativity
{postfix ++,−−}	right-to-left
{prefix ++,−−, unary +,−unary !}	right-to-left
{*, /, %}	left-to-right
{binary +,−}	left-to-right
{<, >, <=, >=}	left-to-right
{==, !=}	left-to-right
{&&,||}	left-to-right
{assignment =, +=,−=, *=, /=, %=	right-to-left

1D arrays, ie lists

int a[10] = {1,2,3,4,5,6,7,8,9,10}; // stores the max 10 ints
int b[10] = {1,2,3,4,5,6,7,8*2}; 
int c[10] = {0}; // inits all elements in container c to 0
int e[] = {1, 2, 3, 4, 5, 6, 7}; // sets max automatically
int f[10] = {[2] = 2, [7] = 9, [9] = 7, [2] = 3};

Resources:

https://www.tutorialspoint.com/c_standard_library/c_function_scanf.htm

https://www.tutorialspoint.com/c_standard_library/c_function_printf.htm

https://www.geeksforgeeks.org/program-for-conversion-of-32-bits-single-precision-ieee-754-floating-point-representation/

Week 3

for, while, do-while loops

comparison operators and conditional expressions (also not tertiary operators expression ? true : false)

No such thing as boolean only exists when including stdbool.h

Week 4

Sorting algorithms

Types in c

sizes

• int (signed) - 32bits/4bytes therefore largest is 2^32-1 or 2,147,483,647
• short - 16 bits
• long - 32/64 bits (system dependent)
• long long (often simplified to ll via definition) - 64 bits
• float - 32 bits
• double - 64 bits
• long double - 80 or 128 bits (mostly used for very high precision calculations like money or aeronautics)

sizeof() finds the size in bytes

char

• signed 128 ($2^7$) bits
• case sensitive
• signed integers of size 1 byte (8 bits)
• Stored as ASCII
• *note all char must be expressed by single quotations ie 'w'
• Double quotations indicate a string type in c, therefore single vs double quotation marks matter

Changing Types

To go from 1 type to another, one can apply as cast ie

int a = 10;
float b = (float) a;

Another way types can change is via "promoting"

The compiler will always promote to the type with more storage

bool → char → short int → int → unsigned int → long int → unsigned long int( → )float → double → long double

Floats

Floats are represented with

• 1 signed bit
• 8 exponent bits
• 23 bits for binary representation (called fraction)

Class example

111:
-> in binary (base-2) system: 1101111
-> left filled w/ 0's: 0000000 00000000 00000000 01101111
-> add sign bit 0: 00000000 00000000 00000000 01101111

111.111:
-> integral part: 1101111
-> fractional part:
0.111 x2 = 0.222 -> 0
0.222 x2 = 0.444 -> 00
0.444 x2 = 0.888 -> 000
0.888 x2 = 1.776 -> 0001    0.776
0.776 x2 = 1.552 -> 00011   0.552
0.552 x2 = 1.104 -> 000111  0.104
0.104 x2 = 0.208 -> 0001110
0.208 x2 = 0.416 -> 00011100 ...

the exponential format (%a): 1.101111 00011100 ... x2^6
the exponent is 01111111 (= 127) + 6 (= 110) = 10000101
add sign bit 0: 0 10000101 101111 00011100 ...

Type def

#define one 1

This is called a macro and will replace every instance of one with 1 literally. Think of this as a find and replace (with spaces on both sides) excluding strings

#typedef int Bool;

Bool is a new data type, and its type is int

Multi-dimensional arrays

instantiated with int a[5][9] and holds 5 rows with 9 columns

Week 5

Functions

# form
return-type function-name ( parameters ) {
    declarationsstatements
}

* note returns value not an array

Use keyword static to declare the minimum length

ie int sum(int a[static10][100], int n)

• length is >= 10
• complier optimizes it

exit() (from <stdlib.h>) exits program

variables only exist in there block (a block is the things surrounded by braces ie { int something })

General format of program should be

#include directives
#definedirectives
type definitions
external variables
function prototypes
definition of main
definitions of other functions

Week 6

Pointers!

• Pointers are unsigned long int that is the address to the memory value

• Therefore can be passed by

• Address operator (&) and dereference operator (*)

• dereference operator returns the value of the memory address

• arrays are like pointers

• pointers can be incremented or decremented

Therefore looping through array with pointers

int sum = 0;
for (p = &a[0]; p < &a[10]; p++) {
    sum+=*p;
}

*note *p++ = *(p++)

gdb

A debugger, see https://www.geeksforgeeks.org/gdb-step-by-step-introduction/

Week 7

Review 1

Week 8

Strings!

'\0' is the null char and signified the end of a string

Strings can be char arrays char a[] or char pointer char *a

*Note no string type like C++ 😭

IO

• scanf skips leading white spaces and reads characters until a white space is encountered

string lib has lots of string functions like

• strcpy - copies 1 string to another
• strlen - len of string
• strcat - concates the first string with the second string (the first string is the final string)
• strcmp - compares 2 strings

Memory

within <stdlib.h> there exist 3 important memory allocation function

malloc() /* allocates a block of memory, no initialization */
calloc() /* allocates a block of memory, clears it */
realloc() /* resizes a previously allocated block of memory */

They all return the pointer to the first byte

(make sure you check to see if it is NULL incase it fails to alloc memory)

Also make sure to free memory at the end with the free() function as c does not manage your memory

Linked list

See https://www.geeksforgeeks.org/linked-list-set-1-introduction/ or https://github.com/Zeyu-Li/c_linked_list

Function pointers

void sort(void (*pf)(int *, int, int), int *array, int i, int j) {
	pf(array, i, j);
	return;
}

Week 9

Preprocessor

These events happen at compile time and changes the code in intermediate step

Preprocessor expressions include

#include
#define
#if, #ifdef, #ifndef, #elif, #else, #endif

• include pastes the library/package into the current code
• see defines
• defines ignores strings when it is a function

#define MK_ID(n) i##n

int MK_ID(1), MK_ID(2);
// becomes
int i1, i2;

Data types

• struct - collection of objects (object like)
• unions - size of largest type member
• enum - set of items like a select one in dropdown

Week 10

Header file

one c file can have a header file usually of cfilename.h where definitions reside

Makefiles

* note very similar to shell script

• First line provides target and dependencies
• 2nd is the execution script
• *note second line has a leading tab
• clean can also be included to remove intermediates and executables

Week 11

Reading Week

Week 12

Review 2

Low level programming

• Bitwise operators of << and >>
• Logic operators of ~, &, ^, |
  • ~ - not, flips all bits
  • & - add (see add truth table)
  • | - or
  • ^ - xor (also known as exclusive or)

Week 13

• linux time command

Keywords

static

• static storage inside block
• Otherwise a internal linkage

extern

• share across multiple files

register

• stores in register (faster than memory)

const

• read only (ie immutable, not immutable)

auto is also a keyword but no one uses it in C, however in C++, it has changed to implied type

Week 14

Review 3

Intro to C++ (can be ignored)

My options on C++

Much better than C especially with the STL including many popular alg and data structures like Stack, Queue, and more (see https://www.geeksforgeeks.org/the-c-standard-template-library-stl/)

But better memory management and quicker to right readable code for recent version of C++, ie with auto, ranged based for loops, classes, and more

* note c can be incorporated into a cpp program

Week 15

Review 4?

Quizzes

Online 20 min quizzes with 15 question open book.

contains trick questions

(11 quizzes total)

Labs

Labs are once a week and genuinely fun most of the time

Time it takes to complete each lab various greatly week by week

(12 labs total)

Assignments

There are two assignments that take plenty of time and are only worth bonus marks

Final

1 two sided piece on paper as cheat sheet. ~40 MC and 10 short answer.

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