Working with 32 bit data types and 8 bit data type in ARM

I am new to ARM LPC2148 micro controller and also new to StackOverflow. I just saw one piece of code in one of the evaluation boards. I am pasting as it is below.

Port pins P0.19 to P0.22 are mapped to D4 to D7 of LCD. The function below is used to send commands to LCD operated in 4 bit mode:

void LCD_Command(unsigned int data)     // This function is used to send LCD commands
{
 unsigned int temp=0;
 EN_LOW();                      // Set EN pin of LCD to to Low
 COMMAND_PORT();
 WRITE_DATA();

 temp=data;
 IO0PIN&=0xFF87FFFF;
 IO0PIN|=(temp & 0xF0) << 15;

 EN_HI();   // Give strobe by enabling and disabling En pin of LCD
 EN_LOW();

 temp=data & 0x0F;
 IO0PIN&=0xFF87FFFF;
 IO0PIN|=(temp) << 19;

 EN_HI();
 EN_LOW();
 while(Busy_Wait());
 Delay(10);
} 

My questions are:

1. 
   

   The variable "data" is already 32 bit wide. Is it efficient to shift the data in this way? Coder could have passed 32 bit data and then masked (&)/ORed (|). Or are there any other impacts?

   
   


2. 
   

   Do we save any memory in LPC21xx if we use unsigned char instead of unsigned int? Since registers are 32 bit wide, I am not sure whether internally any segmentation is done to save memory.

   
   


3. 
   

   Is there any way we can easily map 8 bit data to one of the 8 bit portions of 32 bit data? In the above code, shifting is done by hard coding (<<15 or <<19 etc). Can we avoid this hard coding and use some #defines to map the bits?