Micro Focus Enterprise Developer 3.0 for Visual Studio 2017 > Programming > Mainframe Programming > Assembler Support > Debugging Assembler Applications > Starting the Assembler Debugger

Starting the Assembler Debugger

The method required to start the Assembler Debugger varies depending on how the program or programs are invoked, and the components that make up your application.

Important: All methods require that you first compile your application for debugging. All methods except the Standalone Assembler Program method require that you configure an enterprise server to run the application before debugging the application.

Standalone Assembler Program

To debug a single Assembler program from the command line:

From a 32-bit Enterprise Developer command prompt, change to the directory that contains your Assembler executable file.
Enter the following:
```
run filename.390
```
where filename.390 is the name of your Assembler executable file.

The Assembler Debugger starts in a command window.

Assembler Program Started from JCL

To debug an assembler program that is invoked via JCL, do all of the following from the same 32-bit Enterprise Developer command prompt:

Alternatively, if you are using the command line, to debug an assembler program that is invoked via JCL, do all of the following from the same 32-bit Enterprise Developer command prompt:

Set the following environment variable:
```
es_server_console=y
```
Note: Failure to set this environment variable before starting the enterprise server results in an RTS197 error when the Assembler application is executed.
Start the enterprise server from within the IDE or from the same Enterprise Developer command prompt using the following command:
```
casstart /rServerName
```
In the IDE, submit the JCL that invokes the Assembler program.

The Assembler Debugger starts in a command window when the JCL executes the Assembler program.

CICS or IMS Assembler Application

To debug a CICS or IMS application that is comprised entirely of assembler programs:

From a 32-bit Enterprise Developer command prompt, set the following environment variable:
```
es_server_console=y
```
Note: Failure to set this environment variable before starting the enterprise server results in an RTS197 error when the Assembler application is executed.
Start the server from within the IDE or from a 32-bit Enterprise Developer command prompt:
```
casstart /rServerName
```
From the same 32-bit Enterprise Developer command prompt, start a server execution process:
```
start cassi /rServerName /a
```
On the Visual Studio Just-In-Time Debugger prompt, select the current instance of Visual Studio; then click Yes.
Run the application using a TN3270 terminal emulator.
If you have installed Micro Focus Rumba as part of the Enterprise Developer installation, you can use the Rumba TN3270 Mainframe Display integrated with the IDE or the standalone Rumba Desktop.

The Assembler Debugger starts in a command window.

COBOL and Assembler in a Non-CICS Application

To debug a non-CICS application comprised of both COBOL and Assembler programs:

In Enterprise Developer, associate your enterprise server with the project.
From a 32-bit Enterprise Developer command prompt, set the following environment variable:
```
es_server_console=y
```
Note: Failure to set this environment variable before starting the enterprise server results in an RTS197 error when the Assembler application is executed.
From the same 32-bit Enterprise Developer command prompt, start the server:
```
casstart /rServerName
```
From the IDE, start debugging the application.
Run the application in a 3270 terminal emulator such as Rumba.

The COBOL programs are debugged in the IDE, and the Assembler programs are debugged in the Assembler Debugger, which appears in a separate window.

COBOL and Assembler in a CICS Application

When you have an application that consists of both COBOL and Assembler programs, the COBOL programs are debugged in Enterprise Developer, and the Assembler programs are debugged in the Assembler Debugger, which appears in a separate window.

To debug a CICS application comprised of both COBOL and Assembler programs:

In the IDE, open the project that contains the application you want to debug.
From a 32-bit Enterprise Developer command prompt, set the following environment variable:
```
es_server_console=y
```
Note: Failure to set this environment variable before starting the enterprise server results in an RTS197 error when the Assembler application is executed.
From the same 32-bit Enterprise Developer command prompt, start the server:
```
casstart /rServerName
```
From the same 32-bit Enterprise Developer command prompt, start a server execution process:
```
start cassi /rServerName /a
```
On the Visual Studio Just-In-Time Debugger prompt, select the current instance of Visual Studio; then click Yes.
Run the application in a 3270 terminal emulator such as Rumba.