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This is CS50

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cs50.ly/screen

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ide.cs50.io

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https://cdn.cs50.net/2020/fall/lectures/1/src1/

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This is CS50

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#include <stdio.h>

​

int main(void)�{

printf("hello, world");

}

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#include <stdio.h>

​

int main(void)�{

printf("hello, world");

}

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  • functions
  • conditions
  • Boolean expressions
  • loops
  • ...

​

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correctness

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design

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style

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#include <stdio.h>

​

int main(void)�{

printf("hello, world");

}

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CS50 IDE

ide.cs50.io

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#include <stdio.h>

​

int main(void)�{

printf("hello, world");

}

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01111111 01000101 01001100 01000110 00000010 00000001 00000001 00000000�00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000�00000010 00000000 00111110 00000000 00000001 00000000 00000000 00000000�10110000 00000101 01000000 00000000 00000000 00000000 00000000 00000000�01000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000�11010000 00010011 00000000 00000000 00000000 00000000 00000000 00000000�00000000 00000000 00000000 00000000 01000000 00000000 00111000 00000000�00001001 00000000 01000000 00000000 00100100 00000000 00100001 00000000�00000110 00000000 00000000 00000000 00000101 00000000 00000000 00000000�01000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000�01000000 00000000 01000000 00000000 00000000 00000000 00000000 00000000�01000000 00000000 01000000 00000000 00000000 00000000 00000000 00000000�11111000 00000001 00000000 00000000 00000000 00000000 00000000 00000000�11111000 00000001 00000000 00000000 00000000 00000000 00000000 00000000�00001000 00000000 00000000 00000000 00000000 00000000 00000000 00000000�00000011 00000000 00000000 00000000 00000100 00000000 00000000 00000000�00111000 00000010 00000000 00000000 00000000 00000000 00000000 00000000�...

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input → 

→ output

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source code → 

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source code → 

→ machine code

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compiler

source code → 

→ machine code

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make hello

./hello

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functions, arguments

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printf("hello, world");

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printf("hello, world");

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printf("hello, world");

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printf("hello, world");

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printf("hello, world");

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printf("hello, world");

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functions

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functions

arguments → 

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side effects

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return values, variables

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string answer = get_string("What's your name?\n");

printf("hello, %s", answer);

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string answer = get_string("What's your name?\n");

printf("hello, %s", answer);

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string answer = get_string("What's your name? ");

printf("hello, %s", answer);

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string answer = get_string("What's your name? ");

printf("hello, %s", answer);

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string answer = get_string("What's your name? ");

printf("hello, %s", answer);

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string answer = get_string("What's your name? ");

printf("hello, %s", answer);

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functions

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functions

arguments → 

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functions

arguments → 

→ return value

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string answer = get_string("What's your name?\n");

printf("hello, %s", answer);

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printf("hello, %s", answer);

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printf("hello, %s", answer);

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printf("hello, %s", answer);

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main

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int main(void)�{

​

}

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int main(void)�{

​

}

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header files

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#include <stdio.h>

​

int main(void)�{

printf("hello, world");

}

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#include <stdio.h>

​

int main(void)�{

printf("hello, world");

}

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#include <stdio.h>

​

int main(void)�{

printf("hello, world");

}

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#include <stdio.h>

​

int main(void)�{

printf("hello, world\n");

}

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help50

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style50

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check50

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cd

cp

ls

mkdir

mv

rm

rmdir

...

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types

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bool

char

double

float

int

long

string

...

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get_char

get_double

get_float

get_int

get_long

get_string

...

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format codes

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%c

%f

%i

%li

%s

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%c char

%f float, double

%i int

%li long

%s string

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operators

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+

-

*

/

%

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+ addition

- subtraction

* multiplication

/ division

% remainder

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variables, syntactic sugar

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int counter = 0;

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int counter = 0;

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int counter = 0;

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int counter = 0;

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counter = counter + 1;

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counter = counter + 1;

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counter = counter + 1;

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counter += 1;

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counter++;

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conditions

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if (x < y)�{

printf("x is less than y\n");

}

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if (x < y)�{

printf("x is less than y\n");

}

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if (x < y)�{

printf("x is less than y\n");

}

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if (x < y)�{

printf("x is less than y\n");

}

else

{� printf("x is not less than y\n");

}

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if (x < y)�{

printf("x is less than y\n");

}

else

{� printf("x is not less than y\n");

}

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if (x < y)�{

printf("x is less than y\n");

}

else

{� printf("x is not less than y\n");

}

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if (x < y)�{

printf("x is less than y\n");

}

else if (x > y)

{� printf("x is greater than y\n");

}

else if (x == y)

{� printf("x is equal to y\n");

}

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if (x < y)�{

printf("x is less than y\n");

}

else if (x > y)

{� printf("x is greater than y\n");

}

else if (x == y)

{� printf("x is equal to y\n");

}

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if (x < y)�{

printf("x is less than y\n");

}

else if (x > y)

{� printf("x is greater than y\n");

}

else if (x == y)

{� printf("x is equal to y\n");

}

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if (x < y)�{

printf("x is less than y\n");

}

else if (x > y)

{� printf("x is greater than y\n");

}

else

{� printf("x is equal to y\n");

}

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loops

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while (true)

{

printf("hello, world\n");

}

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while (true)

{

printf("hello, world\n");

}

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while (true)

{

printf("hello, world\n");

}

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while ( )

{

printf("hello, world\n");

}

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while (true)

{

printf("hello, world\n");

}

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for (int i = 0; i < 50; i = i + 1)

{

printf("hello, world\n");

}

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int counter = 0;

while (n > 0)

{

printf("hello, world\n");

i = i + 1;

}

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int i = 0;

while (n > 0)

{

printf("hello, world\n");

i = i + 1;

}

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int i = 0;

while (n > 0)

{

printf("hello, world\n");

i = i + 1;

}

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int i = 0;

while (i < 50)

{

printf("hello, world\n");

i = i + 1;

}

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int i = 0;

while (i < 50)

{

printf("hello, world\n");

i = i + 1;

}

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int i = 0;

while (i < 50)

{

printf("hello, world\n");

i = i + 1;

}

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int i = 0;

while (i < 50)

{

printf("hello, world\n");

i += 1;

}

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int i = 0;

while (i < 50)

{

printf("hello, world\n");

i++;

}

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int i = 1;

while (i <= 50)

{

printf("hello, world\n");

i++;

}

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int i = 50;

while (i > 0)

{

printf("hello, world\n");

i--;

}

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for (int i = 0; i < 50; i = i + 1)

{

printf("hello, world\n");

}

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for (int i = 0; i < 50; i = i + 1)

{

printf("hello, world\n");

}

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for (int i = 0; i < 50; i = i + 1)

{

printf("hello, world\n");

}

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for (int i = 0; i < 50; i = i + 1)

{

printf("hello, world\n");

}

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for (int counter = 0; i < 50; i )

{

printf("hello, world\n");

}

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for (int i = 0; i < 50; i = i + 1)

{

printf("hello, world\n");

}

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for (int i = 0; i < 50; i = i + 1)

{

printf("hello, world\n");

}

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for (int i = 0; i < 50; i = i + 1)

{

printf("hello, world\n");

}

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for (int i = 0; i < 50; i += 1)

{

printf("hello, world\n");

}

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for (int i = 0; i < 50; i++)

{

printf("hello, world\n");

}

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abstraction

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scope

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floating-point imprecision

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integer overflow

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0000

132 of 151

0001

133 of 151

0010

134 of 151

0011

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0100

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0101

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0110

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0111

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1000

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1000

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1 January 2000

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095

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096

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097

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098

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099

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100

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100

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19 January 2038

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This is CS50