COMS W3157 Advanced Programming (AP)
- Take notes on the possible contents of paper that are allowed to be brought in.
bash
- opt
- var symbols
heap/stack
- arguments for execl
Traps
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fork in while loop
- Continuously branching out
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Even if incremented inside a function, the original variable does not change
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exec finishes the code once it is executed
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Even if the incremented value is freed, it may be NULL
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Variables created on the stack within a function call disappear when the scope is exited
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fwrite outputs binary
- Use “rb” instead of “r”
- I want to confirm this
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If the system is already big-endian, we won’t swap the bytes. If the system is little-endian, we swap the bytes to make them big-endian
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If reading something other than a string, use “rb” instead of “r”, “wb” instead of “w”
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When dealing with files, don’t forget to close them
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argv[argc] = Null Pointer (*char) = NULLNULL = false
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socket, bind, connect, listen, accept
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valgrind error types
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c pointer struct union
| Type | Storage size | Value range |
|---|---|---|
| char | 1 byte | -128 to 127 or 0 to 255 |
| unsigned char | 1 byte | 0 to 255 |
| signed char | 1 byte | -128 to 127 |
| int | 4 bytes | -32,768 to 32,767 or -2,147,483,648 to 2,147,483,647 |
| unsigned int | 4 bytes | 0 to 65,535 or 0 to 4,294,967,295 |
| short | 2 bytes | -32,768 to 32,767 |
| unsigned short | 2 bytes | 0 to 65,535 |
| long | 8 bytes or (4bytes for 32 bit OS) | -9223372036854775808 to 9223372036854775807 |
| unsigned long | 8 bytes | 0 to 18446744073709551615 |
1 byte = 8 bit = 2^8 pattern = 256 pattern = 16 ^ 2 pattern = 0x00~0xff
Big little endian check and convert
host = linux: little endian network = tcp/ip: big endian
listen
- non-blocking
bind
- client is not necessary
1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, 65536, 131072, 262144, 524288, 1048576, 2097152, 4194304, 8388608, 16777216,
In order to find the negative binary representation of a number n, you will need to flip all of the bits (in C, you can use the negation operator ’~’ to do this) and add 1.