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convert 16 bit number to 32 bit sign extended number and how to perform <<2 operation

Posted on 2005-04-02
Medium Priority
Last Modified: 2008-02-01

can you show me how will i do the following in c++:

how will i convert 16 bit number to a  32 bit sign extended number.
also, how will i perform <<2 operation.

Question by:sjain1203
  • 2
LVL 86

Expert Comment

ID: 13688569
Um, usually, you would

#ifdef MSC_VER // MS compilers use different type names
typedef __int16 int16_t;
typedef __int32 int32_t;

int16_t i16 = 42;
int32_t i32 = reinterpret_cast<int32_t>(i16);

>>also, how will i perform <<2 operation.

That depends on what you want to do. Can you elaborate? E.g.

int n = 1 << 2; // n will hold 4 now

Author Comment

ID: 13688634
i get an error: " cannot cast from 'short' to 'int' when i execute the above code.

LVL 86

Accepted Solution

jkr earned 2000 total points
ID: 13688657
Sorry, my fault, that should be

#ifdef _MSC_VER // MS compilers use different type names
typedef __int16 int16_t;
typedef __int32 int32_t;

int16_t i16 = 42;
int32_t i32 = static_cast<int32_t>(i16);

BTW, you could also use a "C-style" cast to achieve the same:

int16_t i16 = 42;
int32_t i32 = (int32_t)i16;

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