Character types

Open Server has four character types, CS_CHAR, CS_LONGCHAR, CS_VARCHAR, and CS_UNICHAR:

CS_CHAR corresponds to the Adaptive Server datatypes char and varchar. That is, Server-Library interprets both the server char and varchar datatypes as CS_CHAR. For example, srv_descfmt returns CS_CHAR_TYPE when retrieving the description of a character parameter from a client.

CS_CHAR is defined as follows:
```
typedef char               CS_CHAR;  
```
CS_LONGCHAR does not correspond to any Adaptive Server datatype, but some Client-Library applications may support CS_LONGCHAR. An application can use the CS_DATA_LCHAR capability to determine whether a Client-Library connection supports CS_LONGCHAR.

A CS_LONGCHAR value supports a maximum length of 2,147,483,647 bytes. CS_LONGCHAR is defined as follows:
```
typedef unsigned char      CS_LONGCHAR;
```
CS_VARCHAR does not correspond to any Adaptive Server datatype. For this reason, Open Server routines do not return CS_VARCHAR_TYPE. If a datatype is described as CS_VARCHAR_TYPE, Open Server automatically converts it to a nullable CS_CHAR_TYPE before sending it to a client. CS_VARCHAR_TYPE can only be used when binding program variables. CS_VARCHAR enables programmers to write non-C programming language veneers for Open Server. Typical server applications will not use CS_VARCHAR.

CS_VARCHAR is defined as follows:
```
typedef struct _cs_varchar
```
```
 {
```
```
     CS_SMALLINT          len; 
```
```
     CS_BYTE              str[CS_MAX_CHAR]; 
```
```
  } CS_VARCHAR;
```
where:
- len is the length of the string.
- str is the string itself. Note that str is not a null-terminated string.
CS_UNICHAR corresponds to the Adaptive Server unichar fixed-width and univarchar variable-width datatypes. CS_UNICHAR is a shared, C-programming datatype that can be used anywhere the CS_CHAR datatype is used. The CS_UNICHAR datatype stores character data in the 2-byte Unicode UTF-16 format.

CS_UNICHAR is defined as follows:
```
typedef unsigned char       CS_UNICHAR;  
```