1.

If we know the size of the bytes we want to store, the best approach is to use the fixed size byte array type

To initialize a fixed size byte array, we need to specify the size of how many bytes we would like to store.

bytes1 b1 = hex"41";

Bytes can be initialized with either a hex string hex"41" or a hex value 0X41 which is the letter A according to ASCII.

2.

Fixed size bytes can be passed between smart contracts in the Solidity programming language.

3.bytes and bytes32

Bytes is a dynamic array of bytes. It's shorthand for byte[] and you'll see examples of a bytes being treated as an array in code from time to time. myByte[x]. It can have a length of zero and you can do things like append a byte to the end.

Bytes32 is exactly 32 bytes long. It takes exactly one 32-byte word to represent a bytes32 because there's no need to set any space aside to encode the length. The length is always 32. A bytes with 32 bytes of data needs additional encoding to deal with variable length.

4.Converting to bytes

Converting a string to bytes is a straightforward task. We need to initialize bytes passing in the string type. In return, we get a dynamic array of bytes.

bytes memory stringBytes = bytes("This is string");

If we want to convert to the bytes32 type, we need to go to the assembly level and write the string on the memory.

bytes32 result;

assembly {
  result := mload(add("This is string", 32))
}

Keep in mind that we can write only up to 32 bytes.

5.Converting from bytes

In Solidity language, we can convert back the string value to a dynamic size array of bytes. We can’t convert to fixed string bytes because the string type has an unknown size.

bytes memory bytesData = hex"41";
string memory stringData = string(bytesData);