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Client APIs and tools
You can use the HCL Informix® implementation of client APIs to develop applications for Informix database servers.
ESQL/C Guide
The Informix® ESQL/C Programmer's Manual explains how to use Informix ESQL/C, the Informix implementation of Embedded Structured Query Language (SQL) for C (ESQL/C), to create client applications with database-management capabilities.
What is Informix® ESQL/C?
Informix® ESQL/C data types
These topics contain information about the correspondence between SQL and C data types and how to handle data types in the Informix® ESQL/C program.
Data conversion
Fetch and insert with host variables
Convert numbers and strings

Client APIs and tools
You can use the HCL Informix® implementation of client APIs to develop applications for Informix database servers.
- Change Data Capture API Programmer's Guide
  The Informix® Change Data Capture API Programmer's Guide describes how to program applications to process changed data from HCL Informix databases using the Informix Change Data Capture API.
- Embedded SQLJ for HCL Informix®
  The Informix® Embedded SQLJ User's Guide contains information about using Informix Embedded SQLJ.
- ESQL/C Guide
  The Informix® ESQL/C Programmer's Manual explains how to use Informix ESQL/C, the Informix implementation of Embedded Structured Query Language (SQL) for C (ESQL/C), to create client applications with database-management capabilities.
  - What is Informix® ESQL/C?
    - Informix® ESQL/C programming
    - Compile programs
    - Informix® ESQL/C data types
      These topics contain information about the correspondence between SQL and C data types and how to handle data types in the Informix® ESQL/C program.
      - Choose data types for host variables
      - Data conversion
        Fetch and insert with host variables
        Convert numbers and strings
        Convert floating-point numbers to strings
        Convert BOOLEAN values to characters
        The database server can automatically convert BOOLEAN values between database columns and host variables of the fixchar date type.
        Convert DATETIME and INTERVAL values
        Convert between VARCHAR and character data types
        Informix® ESQL/C can automatically convert VARCHAR values between database columns and host variables of character type char, string, or fixchar.
        Perform arithmetic operations
        When Informix® ESQL/C performs an arithmetic operation on two values, it might need to convert data types if the two values do not have data types that match.
      - Data-type alignment library functions
    - Character and string data types
      These topics explain how to use character data types in the Informix® ESQL/C program.
    - Numeric data types
    - Time data types
      These topics explain how to use date, datetime, and interval data types in the Informix® ESQL/C program.
    - Simple large objects
      A simple large object is a large object that is stored in a blobspace on disk and is not recoverable.
    - Smart large objects
      A smart large object is a data type that stores large, non-relational data objects such as images, sound clips, documents, graphics, maps and other large objects, and allows you to perform read, write, and seek operations on those objects.
    - Complex data types
      These topics explain how to use collection and row data types in the Informix® ESQL/C program.
    - Opaque data types
      These topics explain how to use the lvarchar, fixed binary, and var binary data types to access an opaque data type from the Informix® ESQL/C program. Use these Informix ESQL/C data types to represent an opaque data type as it is transferred to and from Informix.
  - Database server communication
  - Dynamic SQL
  - Appendixes
    This section contains additional reference information.
- GLS User's Guide
  The Informix® GLS User's Guide describes the Global Language Support (GLS) feature available in Informix products.
- API
  The Informix® GLS API Programmer's Guide describes the global language support (GLS) application programming interface (API) available in Informix ESQL/C and HCL Informix DataBlade® modules.
- Informix® Object Interface for C++ Guide
  The Informix® Object Interface for C++ Programmer's Guide describes how to develop HCL Informix client applications by using the object-oriented C++ programming language.
- Informix® ODBC Driver Guide
  The Informix® ODBC Driver Programmer's Manual serves as a user guide and reference for Informix ODBC Driver, which is the Informix implementation of the Microsoft™ Open Database Connectivity (ODBC) interface, Version 3.0.
- .NET provider options
  The Data Server Provider for .NET DB2® provider option is the preferred Informix® provider for developing new applications.
- Informix® JDBC Driver Guide
  The Informix® JDBC Driver Programmer's Guide describes how to install, load, and use Informix JDBC Driver to connect to the Informix database from within a Java™ application or applet.
- Informix International Language Supplement (ILS) User Guide
  These topics include information about the translated user interface files for Informix® UNIX™ products, locales, and code set conversion tables
- Informix® OLE DB Provider Guide
  The Informix® OLE DB Provider Programmer's Guide describes the software requirements for using Informix OLE DB Provider, show how to install and configure the provider for your use, and explain how to use Informix OLE DB Provider to enable client applications, such as ActiveX Data Object (ADO) applications and web pages, to access data on the Informix server.

Convert numbers and strings

Before Informix® ESQL/C can convert a value from one data type to another, it must determine whether the conversion is meaningful.

The following table shows possible conversions between numeric data types and character data types. In this figure, N represents a value with a numeric data type (such as DECIMAL, FLOAT, or SMALLINT) and C represents a value with a character data type (such as CHAR or VARCHAR).

If conversion is not possible, either because it makes no sense or because the target variable is too small to accept the converted value, Informix® ESQL/C returns values that the Results column in the following table describes.

Table 1. Data conversion problems and results
Conversion	Problem	Results
C C	Does not fit	Informix® ESQL/C truncates the string, sets a warning (sqlca.sqlwarn.sqlwarn1 to `W` and SQLSTATE to `01004`), and sets any indicator variable to the size of the original string.
N C	None	Informix® ESQL/C creates a string for the numeric value; it uses an exponential format for large or small numbers.
N C	Does not fit	Informix® ESQL/C fills the string with asterisks, sets a warning (sqlca.sqlwarn.sqlwarn1 to `W` and SQLSTATE to `01004`), and sets any indicator variable to a positive integer. When the fractional part of a number does not fit in a character variable, Informix® ESQL/C rounds the number. Asterisks are displayed only when the integer part does not fit.
C N	None	Informix® ESQL/C determines the numeric data type based on the format of the character value; if the character contains a decimal point, Informix® ESQL/C converts the value to a DECIMAL value.
C N	Not a number	The number is undefined; Informix® ESQL/C sets sqlca.sqlcode and SQLSTATE to indicate a runtime error.
C N	Overflow	The number is undefined; Informix® ESQL/C sets sqlca.sqlcode and SQLSTATE to indicate a runtime error.
N N	Does not fit	Informix® ESQL/C attempts to convert the number to the new data type. For information about possible errors, see the Informix® Guide to SQL: Reference.
N N	Overflow	The number is undefined; Informix® ESQL/C sets sqlca.sqlcode and SQLSTATE to indicate a runtime error.

In Data conversion problems and results, the phrase Does not fit means that the size of the data from the source variable or column exceeds the size of the target column or variable.