c programming help,preprocessor

hi every body
what does this code do ?
im familiar with duty of define preprocessor instruction,but i dont know what does bold section do.
tnks

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my second question is:
in above function why we declare input variable in this method ,and dont declare usual like:
tnks again

#define creates as macro.

In the line mentioned
#define k1 ((uint16_t)0x0000)

A simple k1 can be used in a code when ever ((uint16_t)0x0000) is used.

Using this identifier the code can be made readable.

I would prefer to you something more readable Identifier than k1.

tnks i know, k1 was only for example
as i said i know function of define preprocessor ,my ques is what does do ?
as i know that say declare k1 equal with 0x0000 and 0x0000 is a 2byte size variable(unsigned int ),am i true?
then why we dont write cant compiler know size of constant/var from number of digits?
and we say it to compiler with this method ?
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whats my second ques answer ?
tnks

((uint16_t)0x0000)

With the above line you mention that it is a 16 bit value i.e 2Bytes.

You are typecasting the value to a 16bit where you have only assigned 4bits. Remaining bits are set to zero by type casting as above.

For second question :

There is a called function and calling function.
Called function : When one piece of code invokes or calls a function.
Example voide m1(int1,int2);
Calling funciton : When called by a function, this piece of code tells what needs to be done.
Example void SPI_Init(SPI_TypeDef* SPIx, SPI_InitTypeDef* SPI_InitStruct)

In the above calling function, SPI_TypeDef and SPI_InitTypeDef are defined in the code as structures. SPIx and SPI_InitStruct are initialised to create a temp value

SPIx. a = 123; SPIx.b = 456; ... etc.

In called function.. int1 and int2 initialized in main and are have a scope of using those variables in whole program. These two examples are not the perfect way to look at the called and calling function.

Hope am being clear .....

In

SPI_TypeDef* is a pointer to SPI_TypeDef type and SPI_InitTypeDef* is a pointer to SPI_InitTypeDef type.

SPIx and SPI_InitStruct are other two types of data types. They are defined else where in the code.

You have to post the full code for better answer.