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Suppose you have the variable int num and the pointer int* cell. Does it make a difference for the values stored in cell and num to write cell = &num or *cell = num?
cell = &num
means that the contents/value of cell will be equal to the address of num.
*cell = num
means that the content at the address stored in cell, that is the value to which the pointer is pointing to, will be equal to the value of num.
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I have some materials showing this code. what does code means by making these assignments?
char inputfilename[128];
inputfilename[0] = 0;
char *argv[128];
*argv[1] = 0;
In C, character arrays are terminated by a null character (value 0). In both cases in your example, the code initializes the strings to "empty" (with a terminator in the first element). This would prove useful in any subsequent string operations (strcat, strcpy, etc.).
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I have an input number that it's value is not always consistent, i mean the value change plus 1 or minus 1 and etc. So, i want to compare it with a const but have a small range value, for example a const int Dist that have value between 14 to 16. Is that possible to implement it on C programming? Please help me.
You can set constant for lower bound, and constant for upper bound and check if the value falls within the range.
Pseudocode:
int const LOWER_BOUND = 14;
int const UPPER_BOUND = 16;
if (input <= UPPER_BOUND && input >= LOWER_BOUND)
... logic here ...
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#define SRC_ASCLIN_ASCLIN0_RX (*(volatile Ifx_SRC_SRCR*)0xF0038084u)
Here SRC_ASCLIN_ASCLIN0_RX means ASCLIN(Async/Sync serial LIN Comm) Receive Service Request.
I know that the macro is used to point at the address 0xF0038084u. But I want real time examples.
Am working on UART development on Infineon microcontroller.
The macro, when expanded by the preprocessor, cast the integer literal as an address, a pointer to Ifx_SRC_SRCR, then dereferences the pointer so you can get or set the value of the memory stored at that specific address.
So you could write e.g.
Ifx_SRC_SRCR value = SRC_ASCLIN_ASCLIN0_RX;
or
SRC_ASCLIN_ASCLIN0_RX = some_other_value;
It basically equivalent to doing e.g.
int an_integer = 6;
int *pointer_to_an_integer = &an_integer;
*pointer_to_an_integer = 10; // Equivalent to SRC_ASCLIN_ASCLIN0_RX = some_other_value above
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mid= n / 2;//(where n is 10)
int left[sizeof(mid)];
but compiler allocate space for 4[0,1,2,3] elements, it suppose to allocate for 5[0,1,2,3,4] elements.
what could be the issue?
sizeof mean: the size in memory. int is 4 bytes in memory. so sizeof(int)=4.
You probably want to write int left[mid];
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is there any way how to put integer sized 100 000 into 4 elements of char array? If I use sprintf or itoa, array has 6 elements. I tried to use this, but it didnt work. And is there any way how to put these 4 elements back to integer?
char *s;
int value = 100000;
*((int *)s)=value;
Note that:
int value = 100000;
char *s;
*((int *)s)=value;
dereferences uninitialized pointer s, which causes undefined behavior. You could do:
int value = 100000;
char s[4];
*((int *)&s[0])=value;
just note that this stores value in the memory block "occupied" by charr array (at memory level) unlike sprintf, which would print the value in a form of string (characters representing the number).