Week 5 - CS50cdn.cs50.net/2007/fall/lectures/5/week5.pdf · 2012. 8. 22. · Microsoft PowerPoint -...
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0 Computer Science 50 Introduction to Computer Science I Harvard College David J. Malan [email protected] Week 5
Transcript of Week 5 - CS50cdn.cs50.net/2007/fall/lectures/5/week5.pdf · 2012. 8. 22. · Microsoft PowerPoint -...
0
Computer Science 50Introduction to Computer Science I
Harvard College
David J. [email protected]
Week 5
1
“iPhone / iPod touch v1.1.1 jailbreak code posted”
Image from http://www.engadget.com/2007/10/21/iphone-ipod-touch-v1-1-1-jailbreak-code-posted/.
2
Hexadecimal
0xdeadbeef
3
Passing by Value
void
swap(int a, int b)
{
int tmp;
tmp = a;
a = b;
b = tmp;
}see
buggy3.c
4
Passing by Reference
void
swap(int *a, int *b)
{
int tmp;
tmp = *a;
*a = *b;
*b = tmp;
}see
swap.c
5
The StackRevisited
6
Pointers
int i, j;
int *p;
Image from http://computer.howstuffworks.com/c22.htm.
7
Pointers
p = &i;
Image from http://computer.howstuffworks.com/c22.htm.
8
Pointers
*p = 5;
Image from http://computer.howstuffworks.com/c22.htm.
9
Arrays as Pointersint i;
int a[5];
int *p = a;
Image from http://computer.howstuffworks.com/c22.htm.
seecompare{1,2}.c, pointers{1,2}.c
10
Dynamic Memory Allocationmalloc
// instantiate memo
memo = (long long *) malloc((n+1) * sizeof(long long));
if (memo == NULL)
{
printf("Out of memory!\n");
return 2;
}
[...]
// free up memory
free(memo); seefs4.c, copy.c
11
Memory ManagementRevisited
12
CS 50’s LibraryRevisited
seescanf{1,2,3}.c, ~cs50/pub/releases/cs50/cs50.{c,h}
bool
string
char GetChar();
double GetDouble();
float GetFloat();
int GetInt();
long long GetLongLong();
string GetString();
13
struct(and header files)
seestructs1.c
typedef struct
{
int id;
char * name;
char * house;
}
student;
14
File I/O
seestructs2.c
fopen/fclose
fscanf/fprintf
fread/fwrite
feof
...
15
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Computer Science 50Introduction to Computer Science I
Harvard College
David J. [email protected]
Week 5
